@ A magnetic recording disk which comprises (1) a three-layered laminate consisting of a core layer of a biaxially oriented polyolefinfilm which has a birefringence of not more than 0.01 and an amorphous-region orientation coefficient of not more than 0.2 and two outer layers of a biaxially oriented polyester film adhered to said core layer, and (2) a magnetic layer formed on at least one side of the laminate. The magnetic recording disk of the invention undergoes only slight dimensional changes with variations in humidity and temperature, and the dimensional changes are isotropic in the plane. The disk therefore has an excellent electromagnetic properties such as output fluctuation and outbreak of dropouts caused by the environmental change.