A condensation particle counter is capable of efficiently measuring the number and size of fine particles. The condensation particle counter includes a saturator, a plurality of condensers and a plurality of optical particle counters. The saturator is designed to generate a saturated gas by saturating a gas in which fine particles are suspended with working fluid. The condensers are connected to a downstream side of the saturator to condense the saturated gas so that liquid droplets can grow around the fine particles. The optical particle counters are connected to downstream sides of the condensers to optically detect the liquid droplets supplied from the condensers. Each of the condensers has a condenser tube for interconnecting the saturator and each of the optical particle counters. The condenser tube is provided with a hydrophilic inner surface layer.