Abstract: An apparatus for separating fibers from a fiber aggregate comprises a hollow cylindrical apparatus housing defining therein a dissolving chamber. A partition is disposed in the internal space of the apparatus housing and forms the bottom of the dissolving chamber. The partition defines a plurality of through openings, through which fibers separated from the aggregate passes. The apparatus housing has an aggregate inlet to introduce the aggregate to be dissolved with pressurized air. The pressurized air carrying the aggregates is discharged toward the partition and forms swirl flow in the dissolving chamber. By the swirl flow of the air, the aggregate flows to collide onto the partition with an impact. This impact serves as an energy for causing dispersion or dissolving of the aggregate. The partition is preferably formed with elastically or resiliently deformable material for absorbing impact upon the collision of the aggregate thereonto so as not to cause destroying of each individual fiber.