A thermo-element having incorporated in a case a heat expansion body which expands and contracts according to a change in temperature includes: a piston disposed along the axis direction within the case, protruding outward from the opening on one end side of the case, and advancing and receding as the hear expansion body expands and contracts; a guide member disposed within the case and which slidably holds the piston; and a first valve element fitted to an outside portion of the case, in the side of the case, and opening and closing a fluid flow path. A fit-in section of the first valve element and insertion sections of the guide member inserted within the case are displaced from each other in the axis direction and the radial direction of the case.