Abstract: A cam profile data creation apparatus sets cam profile data in which a phase of a drive shaft is associated with a displacement (set displacement) of a driven shaft, a rotation speed of the drive shaft, and an allowable error for the displacement of the driven shaft. A displacement (predictive displacement) of the driven shaft when the drive shaft rotates at the set rotation speed is found based on the set cam profile data, the set displacement and the predictive displacement are displayed to be comparable, and further a form of the display is changed depending on whether an error between the set displacement and the predictive displacement falls within the range of the allowable error.