A transmitter that generates a transmission signal by oversampling a modulated signal, the transmitter comprising: a modulation unit that performs a modulation process on an information sequence and that generates a constant envelope signal; an interpolation unit that inserts a predetermined number of signals identical in amplitude to signal points of the constant envelope signal between the signal points so that signal points including original signal points are located equidistantly, wherein when it is defined that the signal points of the constant envelope signal are s(k), where k=0, 1,..., n-1, n, n+1,..., and that number of oversampling is V, the interpolation unit inserts (V-1) signal points so as to equally divide a shorter arc out of two arcs each having signal points s(n) and s(n+1) as both ends on an IQ plane by the number V in a case of interpolation between the signal points s(n) and s(n+1); a Fourier transform unit that transforms a signal obtained after the interpolation unit has performed a signal insertion process into a frequency-domain signal; a band-limiting filter unit that performs band limitation on a frequency-domain signal output from the Fourier transform unit; an addition unit that adds an out-of-band signal that is a signal cut by the band-limiting filter unit to an in-band signal that is a signal not cut by the band-limiting filter unit; and an inverse Fourier transform unit that transforms a signal obtained after the addition unit has performed an addition process into a time domain signal, characterized in that the oversampling number V is 4 and the addition unit adds the out-of-band signal to the in-band signal by performing a self-folding operation according to the following equations to: When k<0: when -N/2≤k<0, S _ FOLD k + N = S _ FIL k + N + S _ CUT k when k<-N/2, S _ FOLD k + pN = S _ FIL k + pN + S _ CUT k When k≥0: when 0≤k<N/2, S _ FOLD k − N = S _ FIL k − N + S _ CUT k when k≥N/2, S _ FOLD k − pN = S _ FIL k − pN + S _ CUT k wherein the range of the integer k is defined as -2N ≤ k < 2N, N is a length of the signal s(k), S_FOLD[k] is a signal after being subjected to the self-folding operation, S_FIL[k] is the in-band signal, S_CUT[k] is the out-of-band signal, and p is an integer and selected to satisfy -N/2≤k-pN<N/2 in equation and -N/2≤k+pN<N/2 in equation. a modulation unit that performs a modulation process on an information sequence and that generates a constant envelope signal; an interpolation unit that inserts a predetermined number of signals identical in amplitude to signal points of the constant envelope signal between the signal points so that signal points including original signal points are located equidistantly, wherein when it is defined that the signal points of the constant envelope signal are s(k), where k=0, 1,..., n-1, n, n+1,..., and that number of oversampling is V, the interpolation unit inserts (V-1) signal points so as to equally divide a shorter arc out of two arcs each having signal points s(n) and s(n+1) as both ends on an IQ plane by the number V in a case of interpolation between the signal points s(n) and s(n+1); a Fourier transform unit that transforms a signal obtained after the interpolation unit has performed a signal insertion process into a frequency-domain signal; a band-limiting filter unit that performs band limitation on a frequency-domain signal output from the Fourier transform unit; an addition unit that adds an out-of-band signal that is a signal cut by the band-limiting filter unit to an in-band signal that is a signal not cut by the band-limiting filter unit; and an inverse Fourier transform unit that transforms a signal obtained after the addition unit has performed an addition process into a time domain signal, characterized in that the oversampling number V is 4 and the addition unit adds the out-of-band signal to the in-band signal by performing a self-folding operation according to the following equations to: When k<0: when -N/2≤k<0, S _ FOLD k + N = S _ FIL k + N + S _ CUT k when k<-N/2, S _ FOLD k + pN = S _ FIL k + pN + S _ CUT k When k≥0: when 0≤k<N/2, S _ FOLD k − N = S _ FIL k − N + S _ CUT k when k≥N/2, S _ FOLD k − pN = S _ FIL k − pN + S _ CUT k When k<0: when -N/2≤k<0, S _ FOLD k + N = S _ FIL k + N + S _ CUT k when k<-N/2, S _ FOLD k + pN = S _ FIL k + pN + S _ CUT k when -N/2≤k<0, S _ FOLD k + N = S _ FIL k + N + S _ CUT k when k<-N/2, S _ FOLD k + pN = S _ FIL k + pN + S _ CUT k When k≥0: when 0≤k<N/2, S _ FOLD k − N = S _ FIL k − N + S _ CUT k when k≥N/2, S _ FOLD k − pN = S _ FIL k − pN + S _ CUT k when 0≤k<N/2, S _ FOLD k − N = S _ FIL k − N + S _ CUT k when k≥N/2, S _ FOLD k − pN = S _ FIL k − pN + S _ CUT k wherein the range of the integer k is defined as -2N ≤ k < 2N, N is a length of the signal s(k), S_FOLD[k] is a signal after being subjected to the self-folding operation, S_FIL[k] is the in-band signal, S_CUT[k] is the out-of-band signal, and p is an integer and selected to satisfy -N/2≤k-pN<N/2 in equation and -N/2≤k+pN<N/2 in equation.