A thermal overload relay has a case, a main bimetal bending upon detection of an overload current, a release lever rotatably supported by an adjusting link and rotating according to a shifter displaced in response to the bending of the main bimetals, and a contact reversing mechanism for change-over contacts responsive to a rotation of the release lever. The main bimetal, release lever and contact reversing mechanism are disposed in the case. The contact reversing mechanism has a movable plate, and a reversing spring stretched between the other side of the movable plate and a spring support. The other end of the movable plate and the spring support is positioned opposite a support point. The release lever has a release lever supporting part, a reversing spring pushing part, a cam contact part, and a displacement input part, in which the release lever supporting part is pivoted on the adjusting link.