An IC socket (1) includes an insulative housing (2) and large numbers of contacts (9) received therein. The housing defines arrayed contact receiving cavities (22) for accommodating the contacts. The cavities are arranged in array by first partition walls (24) and second partition walls (25), which are perpendicular to each other. The first partition wall is higher than the second partition wall. Each first partition wall is provided with protruding portions (240) and sunken portions (241), which are alternatively arranged.