A charging system is capable of charging a battery of a biped walking robot while stabilizing the posture of the biped walking robot and also restraining the occurrence of spark discharge or noises. A charger of the charging system for charging the battery provided in the biped walking robot includes a seating and retaining unit for retaining the biped walking robot in a seated posture, a power feeding connector that is fitted to a power receiving connector provided in the biped walking robot when the biped walking robot sits on the seating and retaining unit, and a charging unit having a connection detector for detecting whether the power receiving connector and the power feeding connector are in a connected state, a charging power source for supplying charging current to the battery, and a charging controller that supplies charging current to the battery from the charging power source to charge the battery when the connection detector detects that the power receiving connector and the power feeding connector are in the connected state.