An image reading device can perform fixed-reading processing where image data is read by a fixed-document method and conveyed-reading processing where image data is read by a sheet-through method while a reading module is kept staying at any of a plurality of image reading positions including a reference reading position. A control portion, when a reference second adjustment value for the reference reading position used for shading correction in the conveyed-reading processing is acquired, calculates a second adjustment values for a plurality of image reading positions based on the reference second adjustment value, and when the reference second adjustment value is not acquired and a first adjustment value used for shading correction in the fixed-reading processing is acquired, calculates the second adjustment values for the plurality of image reading positions based on the first adjustment value.