tromagnetic field distributions of electronic and magnetic materials. The signal-to-noise ratio of electron hologram decreases when the electron beam irradiation is reduced to avoid unnecessary charging and damage. Noise in the hologram causes phase errors. To obtain accurate phase information, we propose an aperture optimization of Fourier based phase reconstruction. Our method effectively separates the signal from the noise using an extended Fourier ring correlation. From the experimental results using a simulated electron hologram with low signal-to-noise, it was found that the proposed method reduces the phase error to 41% of the conventional method. When applied to a real hologram, the proposed method achieved smoother phase reproduction.