To provide a method and a device for separating plastic waste by which fractional recovering of foamed bodies can be efficiently attained especially when many foamed bodies coexist in the plastic waste.

Plastic crushed mixture containing foamed body crushed pieces 13 which is charged in a water bath and is agitated to be uniformly dispersed in water, is made to flow together with water through a pipe 9 in a direction. Among plastic crushed pieces flowing through the pipe 9, the foamed body crushed pieces 13 are unevenly distributed and flow at an inwall surface upper side. In the middle of the pipe 9, an opening 9a communicating with a foamed body recovering tank 12 is formed at a part of an upper surface thereof. The foamed body crushed pieces 13 which are unevenly distributed and flow at the inwall surface upper side of the pipe 9 pass through the opening 9a and float up due to buoyancy on a water surface in the foamed body recovering tank 12 housing the opening 9a. The floated foamed body crushed pieces are recovered from the water surface of the foamed body recovering tank.