An auto-focusing device and an electronic image pickup apparatus facilitates realizing a high focusing accuracy and a quick focusing operation simultaneously using an inexpensive plastic lens mount. The auto-focusing device according includes a means for correcting the conversion reference, if necessary, for converting the object distance measured by the open-control range finding means to a focusing position of the focusing lens based on the conversion reference and for moving the focusing lens to the converted focusing position. The electronic image pickup apparatus includes the auto-focusing device.