A bar code scanner for scanning a bar code or bar codes having a plurality of parallel bar symbols recorded in contrastive light reflection colors on a record medium. The scanner has an image sensor comprising a plurality of light responsive elements which are arranged in a straight line and activated one by one. The image sensor is supported within a casing which is carried close to the record medium. The casing is provided with a pair of parallel side guide members which extends orthogonally relative to the light responsive elements to define a scanning region. The parallel side guide members are connected by a transversal guide member which defines a scanning line at the end portions of the parallel side guide members.