Dissociation of protonated methanol cluster ions, (CH3OHH+ (n = 2-23), in collision with He, Ne, or Kr atoms were studied by means of a tandem mass spectrometer equipped with octapole ion guides. The mass spectra of the product ions show that the dominant process is evaporation of CH3OH molecules from (CH3-OHH+. The absolute cross section for the evaporation was measured as functions of the cluster sizes and the collision energy in the range 0.05-100 eV in the center of mass frame. The branching fractions for the product ions were also determined. It is inferred that the evaporation proceed via the collisional excitation and subsequent unimolecular dissociation.