Abstract: A detection device according to a first aspect includes a first arm, a second arm, and a detection unit having two states as output. The first arm and the second arm each have a corresponding pressure receiving portion pushed by one of detection targets and are respectively rotatable about rotation axes as rotation centers along the same straight line such that the first arm and the second arm have different positions when the corresponding pressure receiving portion is pushed and not pushed by one of the detection targets. The output of the detection unit is switched to one of the two states in accordance with the positions of the arms.