An adaptor for inspection of circuit boards includes a wiring board for connection, on a front surface of which a plurality of connecting electrodes are formed correspondingly to electrodes to be inspected, and an anisotropically conductive elastomer sheet detachably arranged on the front surface of the wiring board for connection. The anisotropically conductive elastomer sheet has a surface roughness of 0.5 to 5 .mu.m on its front surface coming into contact with the circuit board, and a surface roughness of at most 0.3 .mu.m on its back surface coming into contact with the wiring board for connection. The wiring board for connection has, on its front surface, an insulating layer formed such that each of the connecting electrodes is exposed, and the insulating layer has a surface roughness of at most 0.2 .mu.m on its front surface.