Photonic mode behaviors are theoretically investigated for a mechanically driven (rotating) microstructure (microdisk). The present calculation clarifies for the first time the extraordinary behaviors of photonic modes, which are induced by the rotating motion of the microdisk. First, whispering gallery modes with twofold degeneracy in the microdisk at rest split off due to the onset of rotation (Sagnac effect). This rotation also excites a number of extra modes that appear to have developed from vacuum states in the microdisk at rest. These modes reveal anticrossing and mergin-regeneration phenomena in the dispersion curves of photon frequency as the rotation speed increases. The light intensity distributions in the microdisk exhibit a variety of metamorphoses according to the rotation speed variations. All of these phenomena can be explained as being caused by the coupling of photonic modes to the rotating motion of the microdisk and the resultant coupling between different photonic states.