An imaging device which assures high-quality image information free from a line noise by extracting line noise information from a taken image, detecting an existence of an extrinsic line noise in the image, and correcting the line noise if it exists. The imaging device comprises a memory circuit for storing image pick-up outputs at imaging of a two-dimensional area sensor comprising photosensors or radiation sensors, an extrinsic line noise detection unit for detecting an extrinsic line noise in the image pick-up outputs stored in the memory circuit, and an arithmetic processing circuit for calculating an output quantity of the detected extrinsic line noise. The line noise is eliminated by correcting the image pick-up outputs on the basis of the obtained output quantity of the extrinsic line noise.