The present invention provides a polyolefin resin foam sheet having an area density of 5 g/m.sup.2 or more and 400 g/m.sup.2 or less, and having a time (t) required for a weight decrease from 90% by mass to 10% by mass, of 9 minutes or more, as measured by thermogravimetric analysis carried out at a heating rate of 10? C./min and a measurement temperature of 23? C. to 550? C. According to the present invention, a polyolefin resin foam sheet can be provided that has a high fire retardancy while maintaining a lightweight property.