Abstract: A charged particle beam writing apparatus according to one aspect of the present invention includes an electrode configured to deflect a charged particle beam, an amplifier configured to apply a deflection potential to the electrode, a diagnostic circuit configured to diagnose the amplifier, a switching circuit arranged between an output of the amplifier and the electrode, and configured to switch the output of the amplifier between the electrode and the diagnostic circuit, an electron optical system configured to irradiate a target object with the charged particle beam deflected by being applied with the deflection potential by the amplifier, a column configured to include therein the electrode and the electron optical system, a first coaxial cable configured to connect an output side of the amplifier with the switching circuit, a second coaxial cable configured to connect the electrode with the switching circuit, a third coaxial cable configured to connect the output side of the amplifier with the diagnosti