A power supply system includes a first energy storage, a second energy storage, a power transmission circuit, and circuitry. The circuitry acquires a request supply amount, a request output amount, and failure detection information. The circuitry controls the power transmission circuit in accordance with the at least one of the request supply amount and the request output amount such that a ratio of an amount of electric power supplied from or to the first energy storage and an amount of electric power supplied from or to the second energy storage is to be a first ratio in a normal operating. The circuitry controls the power transmission circuit in accordance with the at least one of the request supply amount and the request output amount such that the ratio is to be a second ratio which is different from the first ration in a partial failure state.