There is a splicer bed 1 having a leader support 3 arranged on the top thereof. One opening 6 is provided in one end of the leader support 3. A knife mounting base 7 is arranged to project from the opening 6 and provided at one end with a cartridge holder 8. The knife mounting base 7 also has a leader positioning head 10 provided on the other end thereof for determining the position of a leader L. A stationary knife 11 is mounted to the leader positioning head 10. A movable knife 12 is mounted for pivotal movement to the stationary knife 11. A film holddown plate 17 is pivotably mounted to the knife mounting base 7. The knife mounting base 7 is also provided with a pair of punches 28 which are arranged slidable and can be lowered by the film holddown plate 17. In action, before the leading portion of a film F drawn out from a film cartridge P loaded in the cartridge holder 8 is held under the film holddown plate 17, the downward movement of the film holddown plate 17 causes the punches 28 to cut two notches in both side edges of the film F. The leading portion of the film F is trimmed by the downward action of the movable knife 12 and then joined by a strip of splicing tape to the leader L placed on the leader support 3.