A fuel supply device that supplies fuel from a fuel tank to a fuel distribution pipe (18, 20) of an internal combustion engine and injects the fuel from a fuel injection valve (18a to 18d, 20a to 20d) connected to the fuel distribution pipe (18, 20), the device comprising: a main line extending from the fuel tank to the fuel distribution pipe (18, 20); a fuel pump that is arranged in the fuel tank or in the vicinity of the fuel tank, and pressurizes the fuel in the fuel tank and supplies the fuel to the main line; a first return line that returns the fuel from the fuel distribution pipe (18, 20) to the fuel tank; a second return line that is branched from the main line in the vicinity of the fuel pump and returns the fuel from the main line to the fuel tank; a valve mechanism capable of selectively connecting and disconnecting the second return line with respect to the main line; a first pressure regulator arranged in the first return line; and a second pressure regulator that is provided in the second return line and adjusts fuel pressure to a lower level than the first pressure regulator does, wherein the fuel supply device further comprises a control section, wherein, when the engine is in a high-temperature starting state, the control section controls the valve mechanism in such a manner as to disconnect the second return line from the main line, characterized in that the control section: determines whether the operating state of the engine is in a high pressure range, in which a high-pressure fuel needs to be injected, or in a low pressure range other than the high pressure range; controls the valve mechanism in such a manner as to disconnect the second return line from the main line when the operating state of the engine is in the high pressure range; and controls the valve mechanism in such a manner as to allow the second return line to communicate with the main line when the operating state of the engine is in the low pressure range. a main line extending from the fuel tank to the fuel distribution pipe (18, 20); a fuel pump that is arranged in the fuel tank or in the vicinity of the fuel tank, and pressurizes the fuel in the fuel tank and supplies the fuel to the main line; a first return line that returns the fuel from the fuel distribution pipe (18, 20) to the fuel tank; a second return line that is branched from the main line in the vicinity of the fuel pump and returns the fuel from the main line to the fuel tank; a valve mechanism capable of selectively connecting and disconnecting the second return line with respect to the main line; a first pressure regulator arranged in the first return line; and a second pressure regulator that is provided in the second return line and adjusts fuel pressure to a lower level than the first pressure regulator does, wherein the fuel supply device further comprises a control section, wherein, when the engine is in a high-temperature starting state, the control section controls the valve mechanism in such a manner as to disconnect the second return line from the main line, characterized in that the control section: determines whether the operating state of the engine is in a high pressure range, in which a high-pressure fuel needs to be injected, or in a low pressure range other than the high pressure range; controls the valve mechanism in such a manner as to disconnect the second return line from the main line when the operating state of the engine is in the high pressure range; and controls the valve mechanism in such a manner as to allow the second return line to communicate with the main line when the operating state of the engine is in the low pressure range. determines whether the operating state of the engine is in a high pressure range, in which a high-pressure fuel needs to be injected, or in a low pressure range other than the high pressure range; controls the valve mechanism in such a manner as to disconnect the second return line from the main line when the operating state of the engine is in the high pressure range; and controls the valve mechanism in such a manner as to allow the second return line to communicate with the main line when the operating state of the engine is in the low pressure range.