Thermostat device

A thermostat device, comprising, a housing inside which a valve seat is formed;

• a thermo-element having one end inserted inside the housing and performing an expanding/contracting operation in response to a temperature;
• a valve body provided on an outer periphery of the thermo-element and being seated on and separated from the valve seat by the expanding/contracting operation of the thermo-element;
• a spring biasing the valve body toward the valve seat;
• and
• a frame supporting one end of the spring,
• wherein the housing comprises a hollow body having an opening at one end and having the valve seat formed therein, a pair of legs standing up from an opening edge of the hollow body, the pair of legs on which the frame is hooked, and ribs provided at the opening edge and contiguous with both sides of a root of one leg of the pair of legs,
• wherein an outer side surface of the pair of legs is formed in an arc shape when viewed from a tip side of said one leg, and an outer surface of a rib of the ribs is curved or inclined so as to extend from the outer side surface of said one leg toward an inside of a circle connecting the outer side surface of the pair of legs.