Disclosed herewith is a charged particle beam apparatus capable of controlling each of the probe current and the objective divergence angle to obtain a desired probe current and a desired objective divergence angle in accordance with the diameter of the subject objective aperture. The apparatus is configured to include an objective aperture between first and second condenser lenses to calculate and set a control value of a first condenser lens in accordance with the diameter of the hole of the objective aperture so as to obtain a desired probe current and calculate a control value of a second condenser lens setting device in accordance with the diameter of the hole of the objective divergence angle and the control value of the second condenser lens setting device, thereby setting the calculated control value for the second condenser lens setting device to control the objective divergence angle.