A connector is provided having functions for sensing the half-fitted state and improved compactness and workability through a simple construction with few components. The connector includes: a first connector part 2 having a first housing fitted with a contact pin; a second part 21 having a second housing with a contact pin connecting with the aforesaid one; and a rotating ring 15 fitted rotatably to the first or second housing and having locking legs 161 that lock coupling of the two parts. On rotating ring 15, a latching section 181 that inhibits the rotation of the rotating ring and housing where the rotating ring is fitted is provided. Prior to coupling of the two parts, the rotating ring 15 is latched to the housing by the latching sections. During mating-coupling, anti-rotation is terminated by the other part being pushed in, the rotating ring 15 is free to rotate, and coupling of the two parts is locked by the locking legs 161.