NOVELTY - A polymer-transition metal hydride complex where transition metal hydride is bonded to the aromatic ring of a homopolymer or copolymer, and polymer-transition metal halide complexes are new.    USE - As hydrogen storage material useful for manufacturing hydrogen storage device (claimed).    ADVANTAGE - The polymer provides hydrogen storage material which can adsorb or desorb hydrogen under mild condition (i.e. at 25 degrees C, 30 atmosphere; for release at 100 degrees C under 2 atmosphere) as compared to conventional storage materials, and dramatically increase the storage amount. The polymer-transition metal hydride complex as hydrogen storage material provides a large capacity of hydrogen storage in a safe and reversible manner. The complex can bind multiple transition metals per molecule via Kubas binding, between transition metal and hydrogen since it utilizes alkali metal as a strong base to activate the aromatic ring during the course of the preparation, and provides high weight percentage of stored hydrogen per total material, and weight of hydrogen per unit volume. The process provides preparation of the polymer-transition metal hydride under stable production condition in a good yield.    DETAILED DESCRIPTION - A polymer-transition metal hydride complex where transition metal hydride is bonded to the aromatic ring of a homopolymer or a copolymer having at least one repeated unit of formula -(Ar((Y')a)-J)- (I), and polymer-transition metal halide complexes of formula -(Ar1((Y1)p)((MXi)r)-J1)m-(Ar2((Y2)q)-J2)n- (IV) are new.    Ar, Ar1 and Ar2=6-20C aromatic ring;    J, J1 and J2=-O-, -NH-, -S- or -PH-;    Y', Y1 and Y2==halogen, -NO2, -NO, -NH2, -R1, -OR2, -(CO)R3, -SO2NH2, SO2X1, -SO2Na, -(CH2)kSH or -CN;    R1-R3=1-30C alkyl, or 6-20C aromatic ring;    X1=halogen;    k=0-10;    a, p and q=0-4;    M=transition metals having the valence of at least 2;    X=halogen;    r=1 or 2;    i=an inteqer (according to valence of M);    m and n=integers.    Provided that m+n is less than 10 or m+n is greater than or equal to 100000, and ratio of m to m+n is 0.1-1.1. An INDEPENDENT CLAIM is included for preparing polymer-transition metal hydride complex and polymer-transition metal halide complex (IV).