Abstract: A connector includes a tube-shaped male member, a female member, an engagement member, and a checking member. The male member has a ring-shaped convexity. The female member has a substantially cylinder-shaped housing. The housing has a pair of widows having a peripheral end and a peripheral edge. The checking member has a letter C-shaped portion, and a pair of engagement convexities. The engagement convexities has a first engaging portion, a leading-end contacting portion, and an inclined second engaging portion. The first engaging portion engages with the peripheral end of the windows of the housing so as to inhibit the checking member from coming off from the housing in a direction perpendicular to an axial direction before the male member is connected with the female member. The leading-end contacting portion is pressed by the ring-shaped convexity to move outwardly in a radial direction so as to diametrically enlarge the letter C-shaped portion when the fitting of the male member is completed.