PURPOSE: To decrease the number of steps of microprogram and to increase the processing speed of branching, by setting previously a branching destinated address and jumping directly to said address when either one of branching conditions is satisified.

CONSTITUTION: A special microword is read out to a microword reading register 2 from a microword storage device 1, and the instruction of this microword is regarded as a branching instruction. Then an address control circuit 6 sends a control signal to a selector 4 so that the address held in a branching register 3 is selected. The selector 4 selects the address held in the register 4, and the next microword is read out to the register 2 from the device 1 as the next address. When an address is set to the register 3, the circuit 6 has a control so as to set the next address to the contents of an address register 5 after setting a microword to the register 2. At the same time, a set pulse is delivered to a signal line 102 so that the address designated by a microword is set to the register 3 via a signal line 100.