A connector 10 includes a board-side housing 21 to be installed on a circuit board 100, and mating housings 61A, 61B to be connected to the board-side housing 21. The board-side housing 21 includes front and back walls 26, 27, left and right walls 28, 29 and accommodation chambers 32A, 32B arranged between the front and back walls 26, 27 and between the left and right walls 28, 29 and open upward. The mating housings 61A, 61B include protruding portions 78 exposed above the board-side housing 21 and protruding toward both front and back sides beyond the front and back walls 26, 27 with the mating housings 61A, 61B accommodated in the accommodation chambers 32A, 32B.