A transmission circuit (100) according to the present invention includes an RF-IC (110), an EM-IC (120), and a power amplifier (130). The EM-IC (120) includes a DC-DC converter (123), a transistor (124), a low-dropout regulator (121), and a regulator output selector switch (122). After an elapse of a predetermined time from a time when an operation mode of the transmission circuit has switched from a polar modulation mode to a quadrature modulation mode to a time when a power supply voltage for the quadrature modulation mode output from the DC-DC converter (123) stabilizes at a desired value, the regulator output selector switch (122) switches a connection destination of a gate of the transistor (124) to a fixed potential, and outputs as a control voltage the power supply voltage for the quadrature modulation mode output from the DC-DC converter (123).