To improve coupling stability between a cover and an actuator base after assembling without obstructing size reduction by allowing a wall of the cover to exhibit elasticity for giving resilient force to a latching claw engaged with an engaging surface in a coupling portion between the cover and the actuator base.

The housing includes an actuator base 1 and a cover 3. At a plurality of coupling portions between the actuator base 1 and the cover 3, latching claws 41, 42, 43 and 44 at a side of the cover 3 are engaged with engaging surfaces 21a, 22a, 24a and 25a, respectively. In one of the coupling portions, the latching claw 42 is projected inward from a surface of a lower end of a wide wall 33 connected downward to a top plate 31 of the cover 3, thereby the latching claw 42 is displaced against elasticity of the wall 33.