When two threads (strands), for example, are executed in parallel in a processor in a simultaneous multi-thread (SMT) system, entries of a branch reservation station of an instruction control device are separately used in a strand 0 group and a strand 1 group. The data of the strand 0 and the data of the strand 1 are allocated to the respective entries by switching a select circuit. When an entry is released from the branch reservation station, the select circuit switches the strands so that a branch instruction in one strand can be released in order, thereby releasing the entry.