The method of controlling data writing velocity of an optical disk player is capable of correctly writing data on a nonstandard optical disk as well as a standard optical disk. The method comprises the steps of: analyzing a track pitch of an optical disk on the basis of a moving distance of an optical pick-up in a prescribed time and the address thereof when a data writing test is executed in an innermost area of the optical disk; judging if the optical disk is a standard optical disk having a standard track pitch or not; calculating an address of changing data writing velocity on the basis of the analyzed track pitch if the optical disk is a nonstandard optical disk; and changing the data writing velocity when the address to which the optical pick-up irradiates the laser beam reaches the calculated address.