A sampling method comprising: obtaining topographical information about a predetermined wide area by using a first sensor provided on a work machine; selecting a candidate area within the wide area based on the topographical information about the wide area, the candidate area having an area less than an area of the wide area, and setting a movement route based on the topographical information about the wide area, the movement route being a route that allows a distal end portion of an arm provided on the work machine to reach a preparation position without coming into contact with an obstacle, the preparation position facing the candidate area; moving the distal end portion of the arm along the movement route to the preparation position, and thereafter obtaining topographical information about the candidate area by using a second sensor provided on the distal end portion of the arm; and specifying a sampling point based on the topographical information about the candidate area and performing sampling at the specified sampling point, wherein the specifying of the sampling point includes determining whether or not there is an obstacle in the candidate area based on the topographical information about the candidate area, and if it is determined that there is an obstacle in the candidate area, changing the candidate area, whereas if it is determined that there is no obstacle in the candidate area, setting the candidate area as a sampling point and performing sampling at the said sampling point, the second sensor includes a projector configured to project a predetermined reference mark, and obtaining the topographical information about the candidate area includes: projecting the reference mark onto the candidate area; and obtaining the topographical information about the candidate area based on a shape of the reference mark that is displayed on the candidate area by projection. obtaining topographical information about a predetermined wide area by using a first sensor provided on a work machine; selecting a candidate area within the wide area based on the topographical information about the wide area, the candidate area having an area less than an area of the wide area, and setting a movement route based on the topographical information about the wide area, the movement route being a route that allows a distal end portion of an arm provided on the work machine to reach a preparation position without coming into contact with an obstacle, the preparation position facing the candidate area; moving the distal end portion of the arm along the movement route to the preparation position, and thereafter obtaining topographical information about the candidate area by using a second sensor provided on the distal end portion of the arm; and specifying a sampling point based on the topographical information about the candidate area and performing sampling at the specified sampling point, wherein the specifying of the sampling point includes determining whether or not there is an obstacle in the candidate area based on the topographical information about the candidate area, and if it is determined that there is an obstacle in the candidate area, changing the candidate area, whereas if it is determined that there is no obstacle in the candidate area, setting the candidate area as a sampling point and performing sampling at the said sampling point, the second sensor includes a projector configured to project a predetermined reference mark, and obtaining the topographical information about the candidate area includes: projecting the reference mark onto the candidate area; and obtaining the topographical information about the candidate area based on a shape of the reference mark that is displayed on the candidate area by projection. projecting the reference mark onto the candidate area; and obtaining the topographical information about the candidate area based on a shape of the reference mark that is displayed on the candidate area by projection.