Seat belt wearing detection device

A seat belt wearing detection device, comprising:

• a tongue unit supported by a seat belt having a housed state and a pulled-out state;
• a buckle unit provided to a seat, the seat belt being fastened by inserting and holding the tongue unit in the buckle unit;
• a wearing detection unit that detects an insertion and holding state of the tongue unit in the buckle unit;
• a seat belt side communication unit that transmits a detection result of the wearing detection unit via a radio signal;
• a control unit connected to the seat belt side communication unit and the wearing detection unit, the control unit determining a wearing state of the seat belt based on the detection result, and controlling the seat belt side communication unit;
• a vehicle side device that receives the radio signal from the seat belt side communication unit to obtain the detection result, and
• a power supply system that supplies electric power to the seat belt side communication unit, the power supply system including:
• a power storage section that is chargeable and dischargeable;
• a charging section that charges the power storage section;
• and
• a power supply section that supplies electric power to the charging section so as to charge the power storage section when the seat belt is in the housed state.