A composite charged particle beam apparatus comprises an FIB column having an ion beam irradiation axis and an SEM column having an electron beam irradiation axis, the FIB and SEM columns being arranged relative to one another so that the beam irradition axes intersect with each other substantially at a right angle. A sample stage is provided for mounting a sample, and a detector detects secondary particles generated from the sample when irradiated with the ion beam or the electron beam. An observation image formation portion forms an FIB image and an SEM image based on a detection signal of the detector. A display portion displays the FIB image and the SEM image in which a horizontal direction of the sample in the FIB image and said horizontal direction of the sample in the SEM image are the same thereby making it possible for an operator to easily comprehend the positional relationship of the observation image of the sample.