A fluid control device that does not require a replacement space worth the length even when a rod shaped cartridge heater is used, enables maintenance if the replacement space worth the width is formed, and suppresses increase in the installation area involved therewith is provided. A concave part 2a opening to the side is formed in the supporting member 2. A heater member 3 is removably inserted from the side and fixed in the concave part 2a of the supporting member 2. The supporting member 2 is formed into a transverse cross section of a horseshoe shape by overlapping two plate shaped members 21, 22. The heater member 3 is inserted into the concave part 2a formed by two plate shaped members 21, 22 and fixed by a hexagon socket head cap screw 26.