The present invention relates to a magnetic quick mounting unit for construction machines, particularly road pavers, having a positioning mark configured for permanent attachment to a construction machine, an attachment device which can be magnetically attached on the positioning mark, an alignment mark arranged on the attachment device and indicating the alignment of the attachment device, and an alignment aid arranged on the positioning mark, the alignment mark and the alignment aid being configured such that the alignment of the attachment device relative to the construction machine can be read from the relative position of the alignment mark to the alignment aid when the attachment device has been attached on the positioning mark. The present invention further relates to a method for magnetic quick-mounting of an attachment device, particularly a camera, to a construction machine, particularly a road paver, comprising the steps of: attaching a positioning mark with an alignment aid on the construction machine; attaching an alignment mark on the attachment device; magnetically attaching the attachment device on the positioning mark; and aligning the attachment device by means of the relative positions of the alignment aid and the alignment mark. Furthermore, the present invention relates to a construction machine having such a magnetic quick mounting unit.