An imaging plate was used to quantitatively measure the electron diffraction intensities of graphite and polyethylene (PE) crystals. After the signs of the structure factors were assigned by using a direct phasing procedure, potential maps were made in order to determine atomic positions. Peaks corresponding to the carbon atoms in graphite were seen at (0,0), (1/3,2/3) and (2/3,1/3) in the map of the c-axis projection. For PE, hydrogen atoms were resolved in addition to carbon atoms due to the higher scattering powers of hydrogen for electron beam than for X-ray. The setting angle of the molecular chain in the c-axis projection of the unit cell was determined to be 46.0-degrees, which is consistent with the results of X-ray experiments. R-factors were found to be 0.228 and 0.197 for graphite and PE, respectively. It is shown that the high sensitivity, the wide dynamic range, the good linear response and the digital output data of the imaging plate are useful for structure analysis using electron diffraction.