NOVELTY - The apparatus (1) has a fixing base (21) arranged in an inner side of a sealed container i.e. chamber (11), and for holding a battery container i.e. battery cell (12). An electrolyte solution supply part injects electrolyte solution to the battery container. An inner side of the sealed container is maintained in a high-vacuum state by a vacuum pump (15). A noble-gas introduction part supplies noble gas to the inner side of the sealed container. A rare gas cylinder (13) i.e. pressure resistant cylinder, is connected to the sealed container through a pressure control valve.    USE - Apparatus for injecting an electrolyte solution in a battery container e.g. battery cell and battery tin, of a cylindrical-shaped lamination-type lithium ion secondary battery or winding-type secondary battery, and flat-shaped lamination-type secondary battery i.e. flat-shaped pouch-type secondary battery. Uses include but are not limited to electronic terminals such as notebook personal computer and mobile telephone, a plug-in hybrid vehicle (PHV), an electrically driven motorbike, an electric vehicle and large-sized equipments.    ADVANTAGE - The noble-gas introduction part supplies the noble gas to the inner side of the sealed container, so that impregnation state of electrolyte solution in the battery container of the secondary battery can be visualized, permeability of the electrolyte solution in the battery container of the secondary battery can be improved, leakage of X ray can be prevented and overflow of the electrolyte solution from the battery container can be suppressed.    DETAILED DESCRIPTION - The noble gas is a xenon or krypton. INDEPENDENT CLAIMS are also included for the following:    (1) an electrolyte solution injection method    (2) a secondary battery inspection method.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of an electrolyte solution injection apparatus.'(Drawing includes non-English language text)'    Electrolyte solution injection apparatus (1)    Chamber (11)    Battery cell (12)    Rare gas cylinder (13)    Vacuum pump (15)    Fixing base (21)