A cutting device, a cutting method and a printing device are provided. The cutting device performs cutting on a post-printing medium after printing an image data, and includes: a medium transport mechanism configured to transport the post-printing medium in a longitudinal direction thereof; a detection mechanism, configured to detect a cutting position by a first mark and multiple second marks on the post-printing medium, the first mark is for specifying at least one cut position in a transport direction, the second marks are for specifying two cut ranges of the post-printing medium in a width direction, the width direction is orthogonal to the transport direction, and each cut range is shown by two positions corresponding from one end to the other end of the post-printing medium; and a cutting mechanism, configured to cut the post-printing medium in the width direction and in the transport direction of the post-printing medium.