To provide a coil assembly holding structure which securely holds a coil bobbin and a coil yoke in the axial direction and the circumferential direction and reduces the number of components even in a coil assembly increasing its size and weight.

A coil assembly holding structure includes: a coil housing 4; a valve body 3 having a seating surface 3A facing a joining end surface 4A formed around an opening of the coil housing 4; and an elastic member 5. A coil yoke 13 is formed so that a part of a coil bobbin 11 is exposed at one end part side in the axial direction of a coil assembly 2, and a sealing part 5A, held between the seating surface 3A of the valve body 3 and the joining end surface 4A of the coil housing 4, is formed at the outer circumferential side of the elastic member 5. A first holding part, pressed by the coil yoke 13 at one end part side of the coil assembly 2, and a second holding part, pressed by an exposed portion of the coil bobbin 11 exposed from the coil yoke 13, are formed at the inner circumferential side of the elastic member 5.