An iDP interface test method includes transmitting test clocks to an iDP sink device; determining whether or not a link clock lock operation in the iDP sink device is successful based on a measurement result of an HPD signal when a clock lock operation for the test clocks is performed; transmitting test data and arbitrary video data to the iDP sink device if the link clock lock operation in the iDP sink device is successful; determining whether or not a symbol lock operation in the iDP sink device is successful when the symbol lock operation for the test data and the arbitrary video data is performed; and comparing a count result with a predetermined reference value, and determining link stability of the iDP sink device based on the comparison result.