The present invention provides a processor system having a main processor that efficiently executes coprocessor instructions, regardless of the type of each coprocessor to which the main processor is connected. When a coprocessor instruction to instruct execution by a coprocessor is supplied, the main processor determines whether or not the supplied coprocessor instruction has a possibility of having control dependency on a preceding coprocessor instruction being executed by a corresponding one of the coprocessor, in accordance with an instruction field corresponding to the supplied coprocessor instruction. If the supplied coprocessor instruction has the possibility of having the control dependency, the main processor issues the supplied coprocessor to the corresponding one of the processors only after the execution of the preceding coprocessor instruction is completed.