To provide an apparatus for trimming a sealed portion of a resin tube, which excellently carries out the trimming of the sealed portion of the resin tube and prevents occurrence of chipping of cutting edges.

In the apparatus 26 for trimming the sealed portion 2a of the clamp-sealed resin tube 1 by means of a first cutting blade (upper blade 27) and a second cutting blade (lower blade 29) which slide with each other, a guide portion 27b is provided so as to protrude from the tip ends of both sides of the first cutting blade in order to guide the sliding motion of the first cutting blade such that the cutting edge of the first cutting blade coincides with the cutting edge of the second cutting blade but does not engage with each other during the sliding motion.