A direct comparison of the performances of the time‐of‐flight (TOF) atom‐probe mass spectrometer in the linear and the energy‐compensated mode has been carried out using our newly constructed combined‐type TOF atom‐probe field ion microscope. The detectability and the mass resolution were measured using the W(011) plane and the Mo(011) plane, respectively. The results suggest that in the energy compensated‐type mass spectrometer, the use of an einzel lens for focusing the ion beam (called a ‘‘focusing energy compensated‐part’’ in the text) is an effective way to increase the transmittance of ions through the deflector system without lowering mass resolution. It is suggested that this type of TOF atom probe is the best.