A seal structure (36) for housings is configured so that: an annular groove (38) is formed in one end surface (4b1) of the facing end surfaces (4b1, 14c1) of two housings (4, 14); an annular seal member (40) is mounted in the annular groove; and the end surfaces are brought into contact with each other to seal between the housings. The seal structure forms: an annular outer peripheral seal section (66) formed by pressing the outer peripheral surface (42) of the seal member against the outer peripheral wall surface (38a) of the annular groove; and an annular end surface seal section (68) formed by pressing the end surface-side surface (46) of the seal member against the other end surface (14c1) of the housing. The outer peripheral seal section and the end surface seal section form a continuous seal section (74) wherein a seal continues from the outer peripheral wall surface to the other end surface.
