To provide a female-side connector having a lock mechanism which could obtain a favorable fastening force constantly. [Solution] In a female-side connector 10, a central axis 13 of a root 15 in a male screw portion 12 of a female-side lock portion 41 screwing together with a female screw portion 23 of a male-side lock portion 42 in a male-side connector 20 intersects at a predetermined angle relative to a central axis 14 of a thread 16.
