Device and method for reading image, and recording medium for image reading program

The present invention relates to an image reading device and an image reading method for reading an image to be picked up using a line sensor. An image reading device reads an image of an electronic part as an image pickup object with camera having a line sensor. The line sensor comprises a plurality of pixels having a photoelectric transfer element arranged in series. The image reading device selects pixels periodically one by one and outputs image signals. The pixels for outputting image signals are set based on width data of an image pickup area stored on image pickup area storage . The image reading device monitors a relative positional relation between the image pickup object and the line sensor using a pulse of encoder A, and controls writing of the image signal into an image storage with a storage controller based on length data of the image pickup area. This process can remove uselessness of outputting the image signal from an unnecessary range and storing it, and improve efficient image reading.