Rubrene layers with thickness comparable to a visible light wavelength on silver thin film exhibit anomalous photoluminescence (PL) spectra that depend strongly on emission angle. The PL properties demonstrated for rubrene (500 nm)/Ag (50 nm) were modulated from yellow green to red luminescence with an increasing emission angle. The factors influencing the emission-angle-dependent PL spectra are discussed from two viewpoints: spectral modulation of rubrene PL by loss of fluorescence photon energy and additional luminescence resulting from optical interference in the rubrene layer or optical modes excited by rubrene molecules.