A size-selective sampler includes: a base body having a receiving space and a concave surface curved toward the receiving space, wherein the concave surface has opposite first and second sides； an inlet port formed on the first side of the concave surface and communicating with the receiving space； and an outlet port formed on the second side of the concave surface and communicating with the receiving space. The inlet port has a length of at least 20 mm along the first side of the concave surface so as to reduce penetration of particles in an air flow. Further, the particle penetration curve is roughly equal to the ISO curve.
