Abstract: A cap includes a visor having a front edge formed with two first cut lines and having two sides each having a first section formed with a plurality of second cut lines, a mediate section formed with a plurality of third cut lines and a rear section formed with an insert, and a crown removably mounted on the visor and having a first end provided with two opposite oblique plates and a second end provided with two opposite support strips each having a distal end formed with a plug. Thus, the foldable cap is mounted and folded easily and conveniently, thereby facilitating a user using the cap.