To provide a shoe built-in type power generation system that converts a change in load on shoe soles by an up-and-down movement of feet when someone walks or runs wearing shoes into rotational energy efficiently and uses the torque to generate electricity by means of the power generator, and also uses the electricity to keep the environment of the feet comfortable and safe when wearing the shoes, and furthermore, can store excessive electricity.

At the back of shoe soles inside the shoe soles where the heels strike, there are provided a shoe built-in type power generator and a conversion shaft that converts a change in load on the shoe soles by an up-and-down movement of feet while walking or running into rotational energy to supply torque to the power generator. Additionally, a free structure in which a rotor shaft of rotation rotates in a fixed direction even if supply of torque from driving gears is stopped is provided between the rotor shaft of rotation that receives torque from the driving gears of the conversion shaft and driven gears.