A multiplier includes an operation unit that adds or subtracts a first group selected from a current input data, and a second group selected from a next input data corresponding to the first group to generate an operation result, a Booth's encoder that encodes the operation result according to Booth's algorithm, and generates code data, a partial product generation unit that calculates a partial product from the code data as a first partial product, and calculates, in a case where the first group and the second group are specific combination, a second partial product, and an adder that cumulatively adds an output from the partial product generation unit. The specific combination is a combination in which the highest-order bit of each of the first group and the second group is the same value, and the third least significant bit obtained after the subtraction operation is 1.