A process for producing pre-expanded particles, comprising the steps of: impregnating 100 parts by weight of polystyrene type resin particles with a volatile blowing agent in the presence of 0.1 to 2.0 parts by weight of a first antistatic agent to obtain expandable resin particles; and bringing 100 parts by weight of the expandable resin particles into contact with 0.1 to 2.0 parts by weight of a second antistatic agent in the presence of an antifoaming agent, and then pre-expanding the particles, thereby obtaining pre-expanded particles, wherein the second antistatic agent and the antifoaming agent are used in a ratio by weight of 1:0.04 to 1.50.