Ringing of a signal after passing through a low pass filter in an LINC type linear amplifier is remedied. A linear amplifying device includes the linear amplifier including the low pass filter for removing high-frequency components; and an origin avoiding circuit which receives an original input signal and is provided upstream of the linear amplifier. If the original input signal is sampled in the vicinity of an origin, the origin avoiding circuit modifies a sampled value so at to replace the sampled value with a fixed value, and supplies the modified input signal to the linear amplifier.