To provide a user-friendly, inexpensive electricity accumulating unit, by which it is charged efficiently only by carrying and doing an exercise or the like, and maintenance is easily performed when any trouble is caused.

In the electricity accumulating unit, a permanent magnet is moved in a coil of a power generation unit 11, by which a battery is charged by electromagnetic induction electromotive force generated in the coil, through a rectifier, wherein the power generation unit holds the spherical permanent magnet in a disk casing 22 so that it may freely roll and move, and coils 23, 24 intersecting in a cross form are wound around the disk casing. With such a constitution, the permanent magnet rolls and moves in the disk casing in every direction to generate power efficiently.