We present a 532-nm excited Raman imaging study of pentacene thin films (thickness, 2, 5, 10, 20, 50, 100, and 150 nm) prepared on an SiO2 surface. The structure of the pentacene films has been investigated by images and histograms of the ratio (R) of intensity of the 1596-cm−1 band (b3g) to that of the 1533-cm−1 band (ag), which can be used as a marker of solid-state phases: 1.54-nm and 1.44-nm phases. The Raman images showed that island-like 1.44-nm phase domains are grown on the 1.54-nm phase layer from 50 nm, and all the surface of the 1.54-nm phase layer is covered with the 1.44-nm phase layer from 100 nm. The structural disorders have been discussed on the basis of the full width at half maximum of a band in the histogram of the R values for each film. Copyright © 2012 John Wiley & Sons, Ltd.