A digital broadcast transmitting device and an exciter have an AGC function. In a level adjusting unit which receives an input of a baseband digital signal from a modulation processing unit, a comparator generates an error signal from a difference between a level signal obtained by digitizing a feedback signal from a power amplifier by A/D converter and a reference voltage generated by a reference generating unit, and an AGC multiplier/divider carries out digital multiplying/dividing coefficient to the baseband digital signal with or by a gain coefficient such that the error signal becomes 0. Thereby, AGC which controls transmission output from the power amplifier at a fixed level is carried out.