A technology related to a transmission device of an amplitude modulation method is disclosed. In the amplitude modulation transmission device, a transmission data signal transformed into a sinusoidal wave transition form is input to a signal input stage of a cascode power amplifier, and a transmission data signal transformed into another sinusoidal wave transition form is input to a bias power stage of the cascode power amplifier. The transmission data signal transformed into the sinusoidal wave transition form has a sinusoidal wave form in a section in which input data transitions and maintain its previous value in a section in which the input data is maintained.