An instruction fusion calculation device of the present invention includes an instruction fusion detection circuit, an instruction fusion circuit, and a calculator. The instruction fusion detection circuit determines whether or not a fusion of a preceding instruction and a subsequent instruction that have a flow dependence relationship between them can be made. The instruction fusion circuit fuses the preceding instruction and the subsequent instruction to which it is determined by the instruction fusion detection circuit that the instructions can be fused into one instruction. The calculator executes the fused instruction into which the instructions are fused by the instruction fusion circuit to output the calculation result and outputs at least one of the calculation results obtained by executing the preceding instruction and the subsequent instruction as an intermediate result.