Dipole mode excitation of a cavity BPM can be generated not only from a beam oset but also from a beam angle. IP-BPM was designed to be less sensitive to beam angle compared with KEK BPM. The sensitivity to beam angle was estimated with a simulation. We also carried out a beam test with a mechanically inclined BPM block, and observed the beam angle signal. Although there were some problems in the measurement, data and simuration seemed consistent in the overall characteristics.