To enhance quality feeling by suppressing backlash of a lid relative to a box body, and to attain improved assemblability and reduced weight by reducing the number of parts of a slide mechanism.

An in-vehicle storage box is in a form for opening/closing an opening part of the box body by the lid by reciprocatingly sliding the lid relative to the box body by the slide mechanism. The slide mechanism 50 comprises a rail guide 52 fixed to the box body 10; and a slide rail 54 fixed to the lid 30 and guided/slid by the rail guide. The slide mechanism 50 is arranged at a position interposed between the box body 10 and the lid 30 and close to a center than both sides in a direction perpendicular to a slide direction of the lid.