It is well known that poly(N-isopropylacrylamide) (PNIPAM), PNIPAM chains show a phase transition from a coil to globule state at a lower critical solution temperature (LCST). A similar response is expected for surface grafted PNIPAM and such layers may have a number of interesting applications including drug delivery, permeation-controlled filters and controlled/sustained release. In order to control the structure of such layers effectively, it is important to investigate in detail the structural behaviour of immobilized PNIPAM chains responding to stimuli from external environment. In this study, structural changes of PNIPAM chains immobilized on solid surfaces were investigated in aqueous solutions with an atomic force microscope (AFM) and a quartz crystal microbalance with dissipation (QCM-D). By AFM imaging, the transition of the grafted PNIPAM chains from brush to mushroom state was clearly visualized; the surface images of the plate were featureless at temperatures below the LCST, whereas a large number of hemi-spherical structures whose size was order of 100nm were found on the surface above the LCST. Both frequency and dissipation signals obtained using QCM-D showed significant change at around LCST, indicating that PNIPAM underwent a collapse by the dehydration of the chains. A complementary investigation indicated that a similar transition could be observed in solutions of high concentration electrolytes. It was also found that the grafting density of the PNIPAM chains significantly affected significantly the sharpness of the phase transition behaviour of them responding to change in environmental conditions.