The present disclosure relates to a colorimetric humidity sensor and a method of preparing the same, and in the colorimetric humidity sensor that is an ultrafast colorimetric humidity sensor including a colorimetric member including humidity-responsive particles configured in a disordered monolayer arrangement on a substrate, the humidity-responsive particles are amorphous, porous, and polydispersed microspheres, and the colorimetric humidity sensor indicates a color change according to humidity upon light irradiation.