The present disclosure relates to a method for injecting an electrolyte to a pouch secondary battery which includes the steps of: interposing an electrode assembly between a first metal laminate film and a second metal laminate film forming a pouch casing, and sealing the edges of each of the films with an electrolyte inlet left therein, thereby providing a pouch secondary battery; mounting the pouch secondary battery between a first jig and a second jig, which are installed in a jig stand so as to have a controllable interval and form a gap space, with the electrolyte inlet facing up, and injecting an electrolyte through the electrolyte inlet; loading the jig stand to a vacuum chamber; increasing the width of the gap space by moving the first and the second jigs so that the area occupied by the electrolyte may be localized in the lower part of the pouch casing, and then forming vacuum atmosphere; and moving the first and the second jigs while maintaining the vacuum atmosphere so that the width of the gap space may be reduced gradually and the liquid surface of the electrolyte may be lifted gradually to a position higher than the top of the electrode assembly.