A liquid level detection device is configured so as to reduce or eliminate the contact between electrical cords led out of a detection section. A liquid level detection device is provided with: a detection section which detects the position of a liquid surface on the basis of the rotation of a rotation section rotating as a float is displaced; a plate-like mounting plate section, one surface of which is a mounting surface to which the detection section is mounted; a flange section which is mounted to a tank for containing liquid; and first and second electrical cords which are led out of the detection section toward the flange section. A branch section which comprises a through-hole is provided in the mounting plate section. The second electrical cord passes through the branch section and is routed around from the mounting surface side of the mounting plate section to the back surface side thereof.