According to an embodiment, a welding target position measuring device comprises: a groove wall welding part detection means for detecting a groove wall welding part based on a result of the calculation performed by a groove shape change amount calculation means; a weld bead end detection means for detecting a weld bead end based on a result of the calculation performed by a groove shape difference amount calculation means; and a welding target position selection means for obtaining a welding pass number of a subsequent pass in a welding information stored in a welding information recording means and selecting a welding target position of the subsequent pass which differs depending on welding positions based on results of the detection of the groove wall welding part and the weld bead end.