Reduce the physical burden on the patient and realize continuous supply of electricity to the implantable medical device more reliably. An internal power generation system (100) provided in a living body for generating electric power to be supplied to an internal implantable medical device (10), the internal power generation system (100) comprising: an electrode (106) capable of applying a voltage to a muscle tissue (20) at a predetermined site in a living body A movable portion 108 provided movably in a predetermined direction upon detection of contraction of the muscle tissue by application of a voltage to the movable portion, a power generation mechanism 104 for generating an electromotive force in accordance with the movement of the movable portion, Like connecting member 110 which is connected to the other end of the connecting member 110 and is connected to the power generating mechanism, and a control unit 118 which controls the voltage applied to the electrode.患者への身体的負担を軽減した上で、より確実に体内植込み型医療機器への継続的な給電を実現する。生体内に設けられ、体内植込み型医療機器10に供給する電力を発生させる体内発電システム100であって、生体内の所定の部位における筋肉組織20に電圧を印加可能に設けられる電極106と、電極への電圧の印加による筋肉組織の収縮の検出に伴い所定の方向に移動可能に設けられる可動部108と、可動部の移動に伴って起電力を発生させる発電機構104と、一端が可動部と接続され、他端が発電機構と接続される紐状の接続部材110と、電極に印加する電圧を制御する制御部118と、を備える。
