An optical scanner for scanning a document includes a housing, a glass platform, an optical scanning module and a heat dissipating member. The glass platform is disposed on the housing for placing thereon the document to be scanned. The optical scanning module is disposed inside the housing for scanning the document. The heat dissipating member is disposed inside the housing and in contact with a first lateral edge of the glass platform for conducting the heat generated from the optical scanning module to the glass platform such that the heat is then radiated from the glass platform to the outside of the housing.