To provide a lithium secondary cell and its manufacturing method which reduce the deformation of the cell appearance by swelling in high temperatures and the deterioration of the cell performance.

To remarkably improve the deformation of the cell appearance and prevent the deterioration of the cell performance, a manufacturing method for the cell comprises the steps of: forming an electrode assembly by interposing a separator 26 between a positive electrode 16 and a negative electrode 18; encasing the electrode assembly in a cell casing 12; pouring an electrolyte solution (an electrolyte 20) into the cell casing 12; chemically converting the cell composed of the electrode assembly, the cell casing 12 and the electrolyte solution; and sealing the cell while depressurizing the cell so as to hold the pressure inside the cell at 20 kPa-1000 Pa for 10-100 seconds, after the pouring of the electrolyte solution or the chemical conversion.