An arithmetic apparatus comprises a plurality of cascade-connected arithmetic units. Each of the plurality of arithmetic units comprises: a calculator configured to operate in one of a rotation mode of performing a rotation calculation, and a vectoring mode of calculating a rotation angle; and a holding unit configured to hold rotational direction information output from the calculator in the vectoring mode. In addition, when operating in the rotation mode, the calculator performs the rotation calculation on data input from an arithmetic unit in a preceding stage, based on the rotational direction information held in the holding unit.