<p>A fuel supply device (1) supplies fuel via fuel piping (3) to an engine mounted on a fuel tank (2). The fuel supply device (1) has an electric fuel pump (10) for sucking the fuel in the fuel tank and sending it out to the fuel piping (3), a check valve (21) for allowing the fuel to flow only from the fuel pump (10) side to the fuel piping (3) side, and a relief valve (31) placed on the downstream side of the check valve (21) and allowing the fuel to flow only from the fuel piping (3) side to the fuel tank (2) side. The check valve (21) prevents reverse flow of the fuel from the fuel piping (3) to the fuel pump (10) side. When the pressure in the fuel piping (3) increases, the relief valve (31) allows the fuel in the fuel piping (3) to flow to the fuel tank (2) side to prevent an increase in pressure in the fuel piping (3).</p>
