Forward and backward equalization processes are effectively used in a communication system for equalizing a received signal of a frame including a known symbol part. The known symbol part is provided in a position other than both ends of the frame. An equalization filter unit acquires a signal of an equalization process result by performing an equalization filter process based on a signal servingas an equalization process target and a tap gain coefficient. An update unit updates the tap gain coefficient using a predefined algorithm. A first or second transmission unit transmits a received signal posterior or prior to the known symbol part to a first or second memory in a forward direction or reverse order. A first or second control unit performs a forward or backward equalization filter process with the equalization filter unit by receiving memory content transmitted from the first or second transmission unit in the forward direction or reverse order and employing a total or part of the known symbol part contained in the memory content as the equalization process target.