A charged particle beam apparatus includes: an irradiation unit that irradiates a sample with a charged particle beam; an image formation section that detects a charged particle generated from the sample due to the irradiation with the charged particle beam and forms an image based on a signal obtained by detecting the charged particle; an input reception unit that receives an observation condition; a derivation section that derives second observation parameters proper for the observation condition based on the received observation condition and first observation parameters stored in a storage unit; and a control unit that controls the irradiation unit based on the second observation parameters.