Abstract: A power saving device is adapted to be incorporated in a cableless computer mouse for reducing power consumption thereof. The power saving device includes a wheel rotatable in unison with an encoding disk of the mouse and at least one pair of conductive contact members respectively connected to a power source and a microprocessor. The contact members have engaging sections forming a normally open loop. The wheel forms a plurality of alternating conductive and nonconductive sections engaging with the engaging sections of the contact members. The conductive sections are electrically connected to each other and may short the contact members when simultaneously engaging with the engaging sections. A control signal is thus generated and applied to the microprocessor of the mouse. The microprocessor may force the mouse into an idle condition for reducing power consumption after having not received the control signal for a predetermined period of time.