A detection device includes an irradiation unit that irradiates a medium with first irradiation light, a first optical system that has a first incident surface and changes the first irradiation light into second irradiation light, a second optical system that has a second incident surface and changes the first irradiation light into third irradiation light, and a light receiving unit that is provided in a traveling direction of reflection light of the second irradiation light and the third irradiation light, which are specularly reflected by the medium, and receives the reflection light of the second irradiation light and the third irradiation light, which are specularly reflected by the medium, so as to detect a positional deviation amount of an image formed on the medium and detect a density deviation amount of the image formed on the medium.