To reduce the incidence of a bottom crimping failure in a paper cup bottom crimping step.

In the paper cup bottom crimping method for forming the rim of the bottom by tightly winding a bottom member paper around the end part of a barrel member paper formed in a cylindrical shape, the bottom member paper is tightly wound with the help of a plurality of knurling rollers 16. Since pressing time per the unit area of the inner periphery of the paper cup can be set to be long, the bottom crimping process is certainly performed and consequently, the incidence of paper cup leakage trouble attributed to the bottom crimping failure can be diminished.