A signal processing device includes: a transmission path estimator that estimates a first transmission path characteristic of a transmission signal using a vertical signal out of vertical and horizontal signals resulting from being received by a vertical polarization antenna and a horizontal polarization antenna; a transmission path estimator that estimates a second transmission path characteristic of the transmission signal using the horizontal signal; a weight calculator that calculates a first weight for the vertical signal and a second weight for the horizontal signal, using the first transmission path characteristic and the second transmission path characteristic; and a weighting applier that applies weighted summation to the vertical signal and the horizontal signal using the first weight and the second weight.