To provide stacking connector structure capable of surely fitting both connector members.

A recessed part 2 having a shape corresponding to a housing peripheral part 23a of a header side connector 20 is installed in a housing peripheral part 13a of a socket side connector 10. When the socket side connector 10 is fit to the header side connector 20, the housing peripheral part 23a of the head side connector 20 is fit to the recessed part 2. Namely, the housing peripheral part 23a of the header side connector 20 is covered so as to be interposed by the housing peripheral part 13 of the socket side connector 10. Thereby, slanting insertion of the socket side connector 10 can be prevented.