A work machine comprising: a holding head (60; 62) having a component holding tool; a moving device (68; 70; 72) configured to move the holding head in a horizontal direction and an up-down direction; an imaging device having side illumination configured to irradiate a lead of a component held in the component holding tool with light from a side; and a control device, characterized in that the control device includes: a first imaging command section configured to image at least one reference mark installed on a reference mark mounting plate such that the at least one reference mark is provided in an end portion of an imaging range of the imaging device in the horizontal direction and at a position below an imaging position where the lead of the component is imaged in the horizontal direction, wherein the reference mark mounting plate is arranged on a plate member surrounding the imaging range of the imaging device in the horizontal direction, a first calculation section configured to calculate a position of the imaging device based on image data captured by the first imaging command section, a lowering command section configured to lower the holding head such that the lead of the component held by the component holding tool falls within an irradiation range of the side illumination, a second imaging command section configured to image the lead of the component based on reflection light of the side illumination by the lead of the component, and a second calculation section configured to calculate a position of the lead of the component based on the image data captured by the second imaging command section, and the imaging device includes a lens configured to image both the reference mark and the lead of the component. a holding head (60; 62) having a component holding tool; a moving device (68; 70; 72) configured to move the holding head in a horizontal direction and an up-down direction; an imaging device having side illumination configured to irradiate a lead of a component held in the component holding tool with light from a side; and a control device, characterized in that the control device includes: a first imaging command section configured to image at least one reference mark installed on a reference mark mounting plate such that the at least one reference mark is provided in an end portion of an imaging range of the imaging device in the horizontal direction and at a position below an imaging position where the lead of the component is imaged in the horizontal direction, wherein the reference mark mounting plate is arranged on a plate member surrounding the imaging range of the imaging device in the horizontal direction, a first calculation section configured to calculate a position of the imaging device based on image data captured by the first imaging command section, a lowering command section configured to lower the holding head such that the lead of the component held by the component holding tool falls within an irradiation range of the side illumination, a second imaging command section configured to image the lead of the component based on reflection light of the side illumination by the lead of the component, and a second calculation section configured to calculate a position of the lead of the component based on the image data captured by the second imaging command section, and the imaging device includes a lens configured to image both the reference mark and the lead of the component. a first imaging command section configured to image at least one reference mark installed on a reference mark mounting plate such that the at least one reference mark is provided in an end portion of an imaging range of the imaging device in the horizontal direction and at a position below an imaging position where the lead of the component is imaged in the horizontal direction, wherein the reference mark mounting plate is arranged on a plate member surrounding the imaging range of the imaging device in the horizontal direction, a first calculation section configured to calculate a position of the imaging device based on image data captured by the first imaging command section, a lowering command section configured to lower the holding head such that the lead of the component held by the component holding tool falls within an irradiation range of the side illumination, a second imaging command section configured to image the lead of the component based on reflection light of the side illumination by the lead of the component, and a second calculation section configured to calculate a position of the lead of the component based on the image data captured by the second imaging command section, and the imaging device includes a lens configured to image both the reference mark and the lead of the component.