A method of manufacturing a display apparatus includes: preparing a substrate including a pixel circuit region and a driving circuit region; forming a first active layer at the pixel circuit region; forming a second active layer at the driving circuit region; forming gate electrodes that overlap the first active layer and the second active layer, respectively, with a gate insulating layer disposed therebetween; forming a first insulating layer covering the first and second active layers; forming a first contact hole that passes through the first insulating layer until a portion of the first active layer is exposed; heat-treating the substrate where the first insulating layer, in which the first contact hole is formed, is formed; and forming a second contact hole that passes through the first insulating layer disposed on the heat-treated substrate until a portion of the second active layer is exposed.