1. An echo canceller in a communication device comprising a signal processing device performing a subband division process on an input signal, the signal processing device comprising: an analysis filter process unit configured to perform an analysis filter process on real-valued input data decimated by a decimation ratio and to output real-valued data for K subbands, when K=4N, where K is the number of subbands and N is the decimation ratio; and a GDFT/SSB modulation batch process unit configured to perform in batch a GDFT process, which is a Generalized Discrete Fourier Transformation process where a time offset is n 0 , and an SSB modulation process, which is a single sideband modulation process, using (K/2)×K real-valued matrix G 1 (m) represented in an equation ⁢ [ Expression ⁢ ⁢ 1 ] G 1 ⁡ ( m ) = [ cos ⁡ [ 2 ⁢ π 2 ⁢ K ⁢ { ( n 0 - Km 4 ) } ] cos ⁡ [ 2 ⁢ π 2 ⁢ K ⁢ { ( n 0 + 1 ) - Km 4 } ] … cos ⁡ [ 2 ⁢ π 2 ⁢ K ⁢ { 3 ⁢ n 0 + Km 4 } ] cos ⁡ [ 2 ⁢ π 2 ⁢ K ⁢ { 3 ⁢ ( n 0 + 1 ) + Km 4 } ] … … … … cos ⁡ [ 2 ⁢ π 2 ⁢ ⁢ K ⁢ { ( K - 1 ) ⁢ n 0 + K ⁡ ( K - 3 ) ⁢ m 4 } ] cos [ 2 ⁢ π 2 ⁢ ⁢ K ⁢ { ( K - 1 ) ⁢ ( n 0 + 1 ) + K ⁡ ( K - 3 ) ⁢ m 4 } ] … ⁢ ⁢ ⁢ cos ⁡ [ 2 ⁢ π 2 ⁢ K ⁢ { ( n 0 + K - 1 ) - Km 4 } ] cos ⁡ [ 2 ⁢ π 2 ⁢ K ⁢ { 3 ⁢ ( n 0 + K - 1 ) + Km 4 } ] … cos ⁡ [ 2 ⁢ π 2 ⁢ ⁢ K ⁢ { ( K - 1 ) ⁢ ( n 0 + K - 1 ) + K ⁡ ( K - 3 ) ⁢ m 4 } ] ] ⁢ ⁢ ⁢ m = 0 , 1 , … and according to an equation [ X 0 SSB ⁡ ( m ) X 1 SSB ⁡ ( m ) … X K / 2 - 1 SSB ⁡ ( m ) ] = G 1 ⁡ ( m ) ⁡ [ x m ⁡ ( 0 ) x m ⁡ ( 1 ) … x m ⁡ ( K - 1 ) ] ⁢ ⁢ m = 0 , 1 , … [ Expression ⁢ ⁢ 2 ] on the outputted real-valued data for K subbands, x m (0), x m (1),. .. , x m (K−1), from the analysis filter process unit provided that m is a time index of the outputted real-valued data for K subbands from the analysis filter process unit, and to output real-valued subbands data, X 0 SSB (m), X 1 SSB (m),. .. , X K/2−1 SSB (m) for (K/2) frequency channels.