A method for forming cavity in substrate includes setting start position on closed loop line having circumference L for substrate, consecutively irradiating laser from laser device upon board for the substrate such that holes are formed, and moving the device in loop from the start position along the line such that penetrating hole is formed through the board. The start position of first loop is set as base position, the moving includes shifting the start position by distance d after each loop and controlling such that the moving satisfies p=Σdi, m≅L/p and M=m×n, where i=1 to n, n represents number of loops, p represents pitch of the holes, m represents number of the holes in loop, Σdi is distance from the base position for the start position after i-th loop, and M is number of the holes by the loops.