An optical apparatus including an optical functional layer having a high refractive index and a method of manufacturing the optical apparatus are provided. The optical functional layer includes a phase change material that has a first refractive index during heat treatment in a first temperature range and has a second refractive index, which is higher than the first refractive index, during heat treatment in a second temperature range that is higher than the first temperature range. The optical functional layer may be configured to have the second refractive index by using a micro-heater without having to be deposited at a high temperature.