A fixing device includes a heating roller, a non-contact temperature sensor, a first air channel, and a second air channel. The non-contact temperature sensor detects a temperature of the heating roller in a non-contact manner. The first air channel is located between the non-contact temperature sensor and the heating roller. The second air channel is located at a side of the non-contact temperature sensor that is farther from the heating roller. An air velocity in the first air channel is greater than an air velocity in the second air channel.