To increase the overall degree of integration, and to realize a cost reduction by effectively using register circuits which are in a storage circuit and are not used so far.

A semiconductor integrated circuit is provided with a storage circuit 1 which has two or more data input registers 3-a to 3-d, 30-a to 30-d which have two or more input/output ports and are provided by two or more units for each of these input/output ports and have input terminals and output terminals, and writes data in internal storage element portions via the data input registers, and a random logic circuit 25 which is arranged around this storage circuit 1 and comprises a combination circuit. Some ports of the storage circuit are used exclusively for read, and in the ports two or more data input registers 3-a to 3-d which are not used exist. By using two or more selectors 21-a to 21-d and the unused two or more registers 3-a to 3-d in the storage circuit 1, a scan path circuit 24 wherein scan flip-flops are cascade-connected is formed.