The present surface mount technology non-reciprocal circuit element (1) includes a ferromagnetic material (14) placed above a circuit board (11), and a conductor cover (13). The conductor cover (13) is composed of a main unit (12) located above the ferromagnetic material (14) and connecting members (17_1, 17_2, 17_3) for electrically connecting the main unit (12) with transmission lines (18_1, 18_2, 18_3) on the circuit board (11), respectively. The ferromagnetic material (14) and at least one of the connecting members (17_1, 17_2, 17_3) are formed so as to create, in at least one of gaps between the side surface of the ferromagnetic material (14) and each of the connecting members (17_1, 17_2, 17_3), a location where a clearance between a side surface of the ferromagnetic material (14) and the connecting member is a first clearance and a location where it is a second clearance different from the first clearance.