A cooling device for cooling a device mounted on a board, wherein when the side of a surface of the board on which the device to be cooled is mounted is defined as the upper side while the side of the other surface is defined as the lower side in a substantially vertical direction to the board, the cooling device comprises: a heat receiving portion that is arranged on the upper side the device to be cooled for performing heat exchange with the device to be cooled and has a structure in which a liquid coolant passes through the inside thereof; screws having biasing means standing upward on the board; a base having a through hole which the screws having biasing means pass through, and arranged on the upper side of the heat receiving portion; biasing means for biasing the base along the screws having biasing means to thereby press the heat receiving portion against the device to be cooled; a group of circulating system devices (14, 15, 16) forming a closed-loop liquid coolant circulating system together with the heat receiving portion, at least one of the group of circulating system devices being supported to the board by the base and the screws having biasing means; a fan for generating air flow; and a chassis for supporting the fan above the base such that the air flow is blown down to the board, or sucked up from the board, wherein the group of circulating system devices is fixed to the chassis, wherein: the chassis has a cylindrical shape standing upward on the base, the base being fixed to its lower opening, and the fan being fixed to its upper opening; the group of circulating system devices includes a radiator, a pump and a reserve tank, the radiator being arranged within the cylinder below the fan, and the pump and the reserve tank being arranged on the inner surfaces of the cylinder below the radiator so as to face each other; a space is formed between the pump and the reserve tank to provide a ventilation path which allows passage of the air flow; and the air flow passes through the radiator and the ventilation path. a heat receiving portion that is arranged on the upper side the device to be cooled for performing heat exchange with the device to be cooled and has a structure in which a liquid coolant passes through the inside thereof; screws having biasing means standing upward on the board; a base having a through hole which the screws having biasing means pass through, and arranged on the upper side of the heat receiving portion; biasing means for biasing the base along the screws having biasing means to thereby press the heat receiving portion against the device to be cooled; a group of circulating system devices (14, 15, 16) forming a closed-loop liquid coolant circulating system together with the heat receiving portion, at least one of the group of circulating system devices being supported to the board by the base and the screws having biasing means; a fan for generating air flow; and a chassis for supporting the fan above the base such that the air flow is blown down to the board, or sucked up from the board, wherein the group of circulating system devices is fixed to the chassis, the chassis has a cylindrical shape standing upward on the base, the base being fixed to its lower opening, and the fan being fixed to its upper opening; the group of circulating system devices includes a radiator, a pump and a reserve tank, the radiator being arranged within the cylinder below the fan, and the pump and the reserve tank being arranged on the inner surfaces of the cylinder below the radiator so as to face each other; a space is formed between the pump and the reserve tank to provide a ventilation path which allows passage of the air flow; and the air flow passes through the radiator and the ventilation path.