A combined measurement of velocity field and surface pressure distribution around a two-dimensional cylinder in a low-speed wind tunnel was conducted using unsteady pressure-sensitive paint (PSP) and time-resolved particle image velocimetry (PIV). We measured pressure fluctuation on the surface of the cylinder as well as spatial distribution of the vorticity fluctuation behind the cylinder. Then we calculated the spatial distribution of coherence for surface pressure and vorticity. Finally, we determined characteristic decay length of coherence in spanwise direction of the cylinder. We obtained good agreement between the characteristic lengths determined by surface pressure and by vorticity. This agreement implies that the unsteady PSP is potentially a good tool for aeroacoustic analysis.