NOVELTY - The structure has a battery case (75) storing a battery (73) mounted in a motorcycle. Related parts e.g. starter relays (85) and fuse boxes (86), are connected to the battery. The parts are placed in related part mounting portions of a sub-case (83) relative to the case. The sub-case is placed near the battery on an inner side of a main unit (81) of the case. The main unit of the case includes inner walls configured such that outer walls of the sub-case contact the inner walls to enable a connecting hole in the sub-case and a connecting hole in the main unit to be aligned with each other.    USE - Battery case structure for a saddle riding-type motorcycle.    ADVANTAGE - The related parts are placed near the battery so as to achieve a simplified mounting procedure for the related parts, thus reducing time and labor efforts. The structure allows the main unit of the battery case and the sub-case to be fastened to each other by inserting a screw into the connecting holes immediately following the positioning of the sub-case relative to the main unit of the battery case, thus manufacturing the structure in an easy manner. The sub-case is placed upwardly of the battery in the main unit of the battery case so as to place the heavy battery at a lower portion in the battery case, thus achieving a lower center of gravity of the motorcycle and integrating mass. The related part mounting portions extend along inner wall surfaces of the main unit of the battery case so as to allow connection among the related parts to be simplified and the sub-case to be positioned easily relative to the main unit of the battery case. The sub-case is formed in a triangular shape and placed in a triangular space, so that the space can be more effectively used.    DESCRIPTION OF DRAWING(S) - The drawing shows a side elevational view of a main section with a battery case mounted in a vehicle body.    Battery (73)    Battery case (75)    Main unit (81)    Sub-case (83)    Starter relays (85)    Fuse boxes (86)