Power supply device for electric vehicle

An electric vehicle has a removable battery case 20, that can be fitted into a battery pack cover 28. The battery case 20 has a part 19P extending above a battery cell accommodating part, and this part 19P is provided with a handle 34 including a longitudinal grip part 78. The handle 34 is offset to the left or right (here, the right) with respect to the vehicle. A lock device 32 attached to a main frame 3 of the electric vehicle 1 is has a lock pin 323 which can be advanced and retracted by key operations. The part 19P has an engagement hole 62 for accepting the lock pin 323, and the engagement hole 62 is formed being formed at either the front or the back surface (here, the front) of the handle (34). The battery pack can be locked to a vehicle body and can be mounted to and detached from the vehicle body with high operability.