<p>Provided is a resin foam having excellent dust-proof performance particularly under dynamic environments. This resin foam is characterized by having 65% or greater of a thickness recovery ratio that is defined as follows. Thickness recovery ratio: the ratio of a thickness of the resin foam when the resin foam is compressed in an atmosphere having a temperature of 23°C for one minute in the thickness direction in such a manner that the thickness of the resin foam becomes 20% of the initial thickness, the compression is removed in an atmosphere having a temperature of 23°C, and the thickness is measured 1 second after the removal of the compression to the initial thickness of the resin foam.</p>
