A load voltage control device, comprising: a load disposed in a tip portion; a power supply circuit and a controller disposed in a proximal end portion; and a cable connecting the tip portion with the proximal end portion, the cable comprising a first and second power supply lines, the power supply circuit comprising at least one power supply, wherein the controller operates to: obtain a voltage applied to the load based on a voltage applied to an input point of the first power supply line, a current flowing through the first power supply line, a voltage applied to an input point of the second power supply line and a current flowing through the second power supply line; and adjust the power supply voltage by controlling the at least one power supply so that the voltage applied to the load becomes substantially equal to a predetermined reference voltage.