To provide divided bodies for forming a resin molded product that has higher accuracy for positioning of bonding surfaces relative to each other than the prior art.

The divided bodies for forming a resin molded product are a pair of divided bodies 2 and 3 for forming a resin molded product by being superimposed on one another and then subjected to vibration welding. Each of the pair of divided bodies 2 and 3 has a bonding surface 40 for abutment with each other. The bonding surface 40 is provided with a protrusion and recess that form a line pattern parallel in a specific direction, and allows the pair of divided bodies 2 and 3 to move relative to each other along the specific direction when the pair of divided bodies 2 and 3 are superimposed on one another and engage with each other.