A drive transmission device disclosed. The device has an input gear configured to rotate by a driving force from a driving source; a swing gear configured to rotate by a driving force from the input gear, the swing gear being located at a first position when the input gear is rotated in a forward direction and located at a second position that is different from the first position when the input gear is rotated in a backward direction that is a direction opposite to the forward direction; an output gear configured to separate from the swing gear when the swing gear is located at the first position, and that is in contact with the swing gear to be rotated by rotation of the swing gear when the swing gear is located at the second position; and a shaft portion configured to support the swing gear such that the swing gear is movable between the first position and the second position. The swing gear has a guide hole into which the shaft portion is inserted.