The present invention aims to provide a flexible resin foam having excellent shapeability and a resin foam sheet, an adhesive tape, a member for a vehicle, and a member for a building each including the resin foam. Provided is a resin foam having a multitude of cells, the resin foam including: a polyvinyl acetal; and a plasticizer, the resin foam having an elongation strain of 300% or more and a 50% compression stress of 70 kPa or less.