The present application relates to a device (10) for cutting hair. The device has a skin contacting face (13) that is arranged to be placed against a surface of the skin of a user during use. An optical system (20) directs a cutting laser beam (18) across a cutting zone (15) parallel to and spaced from said skin contacting face (13) to cut hairs extending into the cutting zone (15). A laser beam sensor (40) is configured to generate information indicative of one or more optical properties of the cutting laser beam (18). A controller (40) is configured to adjust one or more characteristics of the optical system (20) in dependence on the information generated by the laser beam sensor (40). The present invention also relates to a method of cutting hair and a computer program comprising instructions which, when executed by at least one processor, cause the method to be performed.