The motion guide device has a raceway rail having a rolling-element rolling part; a moving block having a loaded rolling-element rolling part facing the rolling-element rolling part and a rolling-element circulation passage including a rolling-element return passage extending approximately in parallel with the loaded rolling-element rolling part; and a plurality of rolling elements arranged in the rolling-element circulation passage. The moving block has a rolling part made of steel and having the loaded rolling-element rolling part, a mounting part connected to the rolling part, having a mounting surface for mounting the moving block onto a counterpart device and having a specific gravity lower than that of the rolling part, and a return part made of resin and having the rolling-element return passage.