A charged particle beam apparatus includes a database that stores a to-be-used-in-calculation device model for use in estimation of a circuit of a sample and an optical condition under which a charged particle beam is applied to the sample, a charged particle beam optical system that controls the beam applied to the sample under the optical condition, a detector that detects secondary electrons emitted from the sample excited by the application of the beam and outputs a detection signal based on the secondary electrons, and a computing unit that generates a to-be-used-in-computation netlist based on the to-be-used-in-calculation device model, estimates a first application result when the beam is applied to the sample based on the to-be-used-in-computation netlist and the optical condition, and compares the first application result with a second application result when the beam is applied to the sample based on the optical condition.