To provide polypropylene-based resin pre-expandable beads capable of giving, under a heating steam pressure lower than ever, a hard-to-crack in-mold expansion-molded form excellent in the neatness of both the surface and thin-walled part, and seldom causing inside fall even after short-time drying in a box-type shape in particular tending to cause inside fall.

The polypropylene-based resin pre-expandable beads are provided, whose base resin comprises a polypropylene-based resin composition comprising 100 pts.wt. of a polypropylene-based resin, 1-5 pts.wt. of an -olefin-propylene copolymer rubber and 1-20 pts.wt. of a petroleum resin and/or a terpene resin.