NOVELTY - A solid-polymer electrolyte composition contains copolymer (C) having specific repeating units (a,b), and electrolyte salt.    USE - For solid-polymer electrolyte used for ionic-conductive film, and electrochemical devices such as solid-polymer electrolyte battery (all claimed), capacitors, sensors, electroconductive (EC) elements and optoelectric transducers.    ADVANTAGE - The ionic-conductive film using the solid-polymer electrolyte composition, has excellent ion electroconductivity, thermal characteristics, physical characteristic, and fabricability or film-forming property. The solid-electrolyte battery using the solid-polymer electrolyte composition, has excellent charging and discharging characteristic.    DETAILED DESCRIPTION - A solid-polymer electrolyte composition contains copolymer (C) having repeating units (a,b) of formulae (I,II), and electrolyte salt.    R1-R3, R6, R8=H or 1-10C hydrocarbon group, R1 and R3, and R6 and R8 optionally couple to form a ring;    R4a,R4b=H or methyl group;    R5=H, hydrocarbon, acyl or silyl group;    m=1-100;    R7=organic group having at least one functional group chosen from H, 1-10C hydrocarbon, hydroxyl, hydrocarbon oxy, carboxyl, acid-anhydride, amino and ester group, carboxyl, epoxy, acid-anhydride and amino group;and    R9=organic group having at least one functional group chosen from hydroxyl, carboxyl, epoxy, acid-anhydride and amino group.    INDEPENDENT CLAIMS are included for the following:    (i) solid-polymer electrolyte, which contains copolymer (C) and electrolyte salt;    (ii) polymer (A1), which has polymer segment (P1) having ionic conductivity, polymer segment (P2) which does not have ionic conductivity, and crosslinked-polymer segment (P3), arranged in the order of P3, P2, P1, P2 and P3;    (iii) solid-polymer electrolyte battery, which comprises solid electrolyte formed into film using the solid-polymer electrolyte composition, or solid-polymer electrolyte composition, and electrode;    (iv) ionic-conductive film, which is film containing polymer having polymer segments (P1,P2), and crosslinked-polymer segment (P4);    (v) copolymer, which has block chain (A) having repeating unit of formula (I), block chains (B1,B2) having repeating unit of formula (II), and block chains (C1,C2) having repeating unit (c) of formula (III); and    (vi) manufacture of the copolymer, which involves performing living-radical polymerization using transition-metal complex as catalyst, polymerization initiator and/or organic halogen compound having halogen atom.    R1-R3, R4a, R4b, R5-R9, m=same as defined above;    R10-R12=R1;and    R13=aryl or heteroaryl group.    DESCRIPTION OF DRAWING(S) - The graph shows the relation between discharge capacitance and voltage of the solid-electrolyte battery.