A method of producing a composite sheet having a foam layer of a first polyolefin-based resin and a surface layer of a second polyolefin-based resin provided on at least one side of the foam layer and containing a polymeric antistatic agent. The method includes coextruding through die a first melt containing the first polyolefin-based resin and a physical blowing agent and a second melt containing the second polyolefin-based resin, the polymeric antistatic agent and a volatile plasticizer to obtain the composite sheet. The amount of the polymeric antistatic agent is 4 to 100 parts by weight per 100 parts by weight of the second polyolefin-based resin and the amount of the volatile plasticizer is 5 to 50 parts by weight per 100 parts by weight of a total amount of the second polyolefin-based resin and the polymeric antistatic agent. The second polyolefin-based resin has a crystallization temperature of Ta [.degree. C.] and a melt viscosity of Ma [Pas], while the polymeric antistatic agent has a crystallization temperature of Tb [.degree. C.] and a melt viscosity of Mb [Pas], wherein Ta, Tb, Ma and Mb satisfy the following conditions: Tb<(Ta+30.degree. C.) Mb