The present invention aims to provide a resin foam, a resin foam sheet, an adhesive tape, a member for a vehicle, and a member for a building that are capable of exhibiting very high sound insulation properties. Provided is a resin foam having a multitude of cells, the resin foam containing: a thermoplastic resin; and a plasticizer, the resin foam having a minimum loss factor of a primary anti-resonance frequency in the range of 20° C. to 60° C. of 0.05 or higher and a secondary anti-resonance frequency in the range of 20° C. to 60° C. of 300 to 800 Hz as measured by mechanical impedance measurement (MIM) in conformity with JIS G0602.