A valve device including: a body including a gas passage through which gas flows and an accommodation recess that is a stepped circular recess and includes an outer recessed portion that opens on the side surface of the body and communicates with the gas passage; a valve mechanism which controls flow of the gas flowing through the gas passage and which includes a sleeve including a cylindrical portion and a bottom portion, a movable core provided in the cylindrical portion so as to be movable in an axial direction of the cylindrical portion, a fixed core fixed to a portion of the cylindrical portion that is closer to an opening of the cylindrical portion than the movable core is, and a solenoid provided on an outer periphery of the cylindrical portion; and a cover fixed to the body such that the cover covers the accommodation recess, the valve device characterized in that: the solenoid protrudes from the accommodation recess; the cover includes a cover recess that opens toward the accommodation recess; the diameter of the cover recess is substantially equal to the inner diameter of the outer recessed portion; and the valve mechanism is assembled to the body such that the valve mechanism is accommodated in the accommodation recess with a portion of the valve mechanism protruding from the accommodation recess and the portion of the valve mechanism is accommodated in the cover recess. a body including a gas passage through which gas flows and an accommodation recess that is a stepped circular recess and includes an outer recessed portion that opens on the side surface of the body and communicates with the gas passage; a valve mechanism which controls flow of the gas flowing through the gas passage and which includes a sleeve including a cylindrical portion and a bottom portion, a movable core provided in the cylindrical portion so as to be movable in an axial direction of the cylindrical portion, a fixed core fixed to a portion of the cylindrical portion that is closer to an opening of the cylindrical portion than the movable core is, and a solenoid provided on an outer periphery of the cylindrical portion; and a cover fixed to the body such that the cover covers the accommodation recess, the valve device characterized in that: the solenoid protrudes from the accommodation recess; the cover includes a cover recess that opens toward the accommodation recess; the diameter of the cover recess is substantially equal to the inner diameter of the outer recessed portion; and the valve mechanism is assembled to the body such that the valve mechanism is accommodated in the accommodation recess with a portion of the valve mechanism protruding from the accommodation recess and the portion of the valve mechanism is accommodated in the cover recess. the solenoid protrudes from the accommodation recess; the cover includes a cover recess that opens toward the accommodation recess; the diameter of the cover recess is substantially equal to the inner diameter of the outer recessed portion; and the valve mechanism is assembled to the body such that the valve mechanism is accommodated in the accommodation recess with a portion of the valve mechanism protruding from the accommodation recess and the portion of the valve mechanism is accommodated in the cover recess.