Safety knife with a blade that can be replaced and where access to the cutting edge of the blade is limited so as to reduce the risk of injury to a user, comprising a blade piece with a blade arranged between a guard and a fixation and an oblong knife body comprising a holder and a partly flat insert for rigidly holding the blade piece near a proximal end, wherein said insert having rails on both sides of the flat part at least near the proximal end, said holder including a depression near the proximal end for receiving the fixation and a channel extending from the proximal end towards the distal end at least beyond the depression for receiving at least the flat part of the insert, said channel having grooves on each side starting at the proximal end for receiving the rails.