To provide a debugging device for measuring a circuit module in a state close to the actual usage state of a circuit module and for performing measurement without causing the unexpected change in a waveform even in a circuit module operating with a high-speed signal.

A debugging device 1 can be freely attached to or detached from a main substrate being arranged in the casing of an electronic device and performs debugging by measuring the electrical characteristics of a circuit module where electronic parts are incorporated. The debugging device 1 is provided with an extension means 2 for essentially taking out circuit modules 44 (44-1-44-7) from a casing 41 while it is electrically connected to a main substrate 42, and a relay means 3 that is connected to the extension means 2 for connecting the circuit modules 44.