There is provided an apparatus for joining films wherein a rear end portion of a preceding film and a front end portion of a trailing film are mutually joined without using a joining material such as an adhesion tape or the like to sufficiently contribute the joint portion to heat seal likewise the other portions of the films and realize excellent liquid tightness and airtightness of the joint portion itself and also tensile strength required for the film itself is given to the joint portion. The apparatus comprises a fuse seal means arranged in the vicinity of a running path of the preceding film, a film-holding means holding the front end portion of the trailing film at a side opposite to the seal means with respect to the running path, an insert plate pushing the front end portion of the film held by the film-holding means into the seal means together with the preceding film, and an extra film removing means clamping a turnup portion of the preceding film pushed over the seal means by the insert plate and separating from a fuse-sealed portion.