A sheet length measurement apparatus including: a rotating member that comes in contact with a recording sheet conveyed on a conveying path, and rotates along with the conveyance of the recording sheet; a rotation amount detector that detects a rotational amount of the rotating member; a fixing support member that fixedly supports an rotating shaft of the rotating member at a fixed position; an opposed member that is disposed opposite to the rotating member so as to hold the recording sheet between the rotating member and the opposed member, the opposed member being disposed so that the rotating member rotates along with the conveyance of the recording sheet; and a support member that supports the opposed member in a movable state in a direction to separate from or come in contact with a surface of the recording sheet.