To obtain an olefin resin composition, e.g. including a propylene resin having flame retardance, mainly used for interior material for vehicles and processed into a sheet, especially a thick sheet.

This flame-retardant olefin resin composition is obtained by adding ethylene-acrylic ester.acid anhydride as a compatibilizer in an amount of 5 pts.wt. based on 100 pts.wt. mixed resin to a mixed resin of 10-40wt.% PVC-based flame-retardant blend comprising 100 pts.wt. vinyl chloride resin, 8.5 pts.wt. antimony trioxide, 5-15 pts.wt. plasticizer, 3 pts.wt. stabilizer and 1 pts.wt. lubricant mixed with 90-60wt.% propylene resin.