A Doherty amplifier comprising: a transistor for a carrier amplifier; a transistor for a peak amplifier; an input phase adjustment line that is a line that adjusts a phase of a signal input to the transistor for the peak amplifier with respect to the transistor for the carrier amplifier; a transmission line connected between an output terminal of the transistor for the carrier amplifier and an output terminal of the transistor for the peak amplifier; a stub that is connected in parallel to the output terminal of the transistor for the peak amplifier and that is capacitive and inductive in a working frequency band; and an output matching circuit connected to the output terminal of the transistor for the peak amplifier and the transmission line at an output combination point, and an output load, the output matching circuit to transform an impedance of the output load into an impedance, as viewed from the output combination point, lower than the impedance of the output load, wherein the transmission line has an electrical length of less than 90°, wherein an output capacitance of the transistor for the carrier amplifier and an output capacitance of the transistor for the peak amplifier are connected via the transmission line having an electrical length of less than 90°, so that the transistor for the carrier amplifier and the transistor for the peak amplifier are configured as being connected via a transmission line having an electrical length of 90° required for their Doherty operation, wherein the output capacitance of the transistor for the carrier amplifier is connected directly to one terminal of the transmission line and the output capacitance of the transistor for the peak amplifier is connected directly to another terminal of the transmission line, wherein the transmission line has a characteristic impedance higher than a real part of an output impedance of the transistor for the carrier amplifier, and wherein the stub is an open stub having an electrical length of an integral, n, multiple of 180° at one frequency in the working frequency band, or the stub is a short stub (14, 15) which includes a transmission line having an electrical length shorter than the integral, n, multiple of 180 degrees by 90 degrees and a capacitor short-circuited at the center frequency and having one end which is connected to ground and the other end connected to the transmission line, wherein the sum (θ SUM) of the electrical lengths of the transmission line, the stub, and the input phase adjustment line which are necessary for Doherty operation is a value within the range expressed in the following equation: 90 ∗ 2 n + 1 < θ SUM < 90 ∗ 2 n + 2. a transistor for a carrier amplifier; a transistor for a peak amplifier; an input phase adjustment line that is a line that adjusts a phase of a signal input to the transistor for the peak amplifier with respect to the transistor for the carrier amplifier; a transmission line connected between an output terminal of the transistor for the carrier amplifier and an output terminal of the transistor for the peak amplifier; a stub that is connected in parallel to the output terminal of the transistor for the peak amplifier and that is capacitive and inductive in a working frequency band; and an output matching circuit connected to the output terminal of the transistor for the peak amplifier and the transmission line at an output combination point, and an output load, the output matching circuit to transform an impedance of the output load into an impedance, as viewed from the output combination point, lower than the impedance of the output load, wherein the transmission line has an electrical length of less than 90°, wherein an output capacitance of the transistor for the carrier amplifier and an output capacitance of the transistor for the peak amplifier are connected via the transmission line having an electrical length of less than 90°, so that the transistor for the carrier amplifier and the transistor for the peak amplifier are configured as being connected via a transmission line having an electrical length of 90° required for their Doherty operation, wherein the output capacitance of the transistor for the carrier amplifier is connected directly to one terminal of the transmission line and the output capacitance of the transistor for the peak amplifier is connected directly to another terminal of the transmission line, wherein the transmission line has a characteristic impedance higher than a real part of an output impedance of the transistor for the carrier amplifier, and wherein the stub is an open stub having an electrical length of an integral, n, multiple of 180° at one frequency in the working frequency band, or the stub is a short stub (14, 15) which includes a transmission line having an electrical length shorter than the integral, n, multiple of 180 degrees by 90 degrees and a capacitor short-circuited at the center frequency and having one end which is connected to ground and the other end connected to the transmission line, wherein the sum (θ SUM) of the electrical lengths of the transmission line, the stub, and the input phase adjustment line which are necessary for Doherty operation is a value within the range expressed in the following equation: 90 ∗ 2 n + 1 < θ SUM < 90 ∗ 2 n + 2.