The present invention provides a method for calibrating verticality of a particle beam. The method includes: providing a baseplate having a first sensor and a second sensor; emitting the particle beam to the first sensor of the baseplate from an emitter, such that a first datum is collected when the first sensor receives the particle beam; emitting the particle beam to the second sensor of the baseplate from the emitter, such that a second datum is collected when the second sensor receives the particle beam; calculating a first calibrating datum based on the first datum and the second datum; and adjusting the baseplate or the emitter based on the first calibrating datum if the first calibrating datum is out of a first predetermined range.