Abstract: A microcomputer including a built-in storage portion capable of executing an evaluation program by an ICE through a simple operation also when the evaluation program cannot be written in the built-in ROM is obtained. A debugging circuit (2) outputs a reset vector selection signal (S2) indicating generation of a reset vector (V1/V2) in response to a control signal (S1) indicating a normal mode/a RAM starting mode, and a reset circuit (3) generates a reset vector (V1/V2) indicating a starting address (A1/A2) after reset cancellation by indication of the reset vector selection signal (S2). The microcomputer can be set to execute the evaluation program from the starting address (A2) on a RAM area (5) after reset cancellation by registering the evaluation program (start address=starting address (A2)) in the RAM area (5) from the ICE through the debugging circuit (2) and thereafter supplying a control signal (S1) indicating the RAM starting mode to the debugging circuit (2).