An electric connecting device of the present invention includes: a first connector having a first housing 22; a second connector having a second housing 42; and a metal latch 5. The first housing 22 has a cylindrical fitting 23, and the second housing 42 has a fitting receiver. On an exterior surface 23s of the fitting 23 are formed four ribs 24 each projecting in a radial direction of a center portion 23c of the fitting 23. An interior surface of the fitting receiver on the other hand has four recesses for respectively fitting therein the four ribs 24, during the connected state. The four ribs 24 includes two ribs 24 which are disposed across from each other over the center portion 23c, along a single line extending through the center portion 23c, when viewed from the connecting direction.