To provide a highly operable mouse for securing a function which performs the predetermined amounts of power generation by the kinetic energy of a mouse ball by preventing the deterioration of the rotatability of the mouse ball as much as possible and its power generating mechanism.

This mouse is configured of a power generating part M constituted of a power transmitting rotary body 21 to be brought into contact with a mouse ball 1 so as to be rotated and a rotary shaft 30 to be rotated by the rotary power of the power transmitting rotary body 21, a permanent magnet 4 mounted on the rotary shaft 30 and a power generating part G constituted of a plurality of power generating coils 52 set on a base 51 faced to the permanent magnet 4, and arranged so as to be made to correspond to the rotary orbits of the magnetic electrodes 411, 412, 421 and 422 of the permanent magnet 4. Then, this mouse is provided with a slide member 43 capable of adjusting a gap dimension between the permanent magnet 4 and the power generating coil 52 in the power generating part G.