States of LSI internal signals (100 to 107) are monitored. Signal name information (31), signal state information (32), and information (33) about time in an LSI when a signal undergoes a state transition, are packetized and output as trace information (10) to the outside. In a development supporting device, the trace information (10) is decoded, the time information of the LSI is converted into real-time information, and based on the resultant information, a waveform of an LSI internal signal is reproduced. A plurality of LSI internal signals can be traced using terminals (16) the number of which is smaller than the number of the signals to be traced.