A laser machining apparatus, comprising: a machining head configured to emit a laser beam; a focusing lens configured to focus the laser beam to irradiate a sheet metal with the laser beam so as to form a beam spot (Bs) on a surface of the sheet metal; a moving mechanism (22, 23) configured to relatively move the machining head with respect to the sheet metal, along the surface of the sheet metal; a beam vibration mechanism configured to vibrate the laser beam when the sheet metal is cut by the irradiation of the sheet metal with the laser beam while the machining head is relatively moved by the moving mechanism (22, 23); characterised in that the laser machining apparatus further comprises: a focal point moving mechanism configured to move a focal point of the laser beam with which the sheet metal is irradiated, in an orthogonal direction orthogonal to the surface of the sheet metal; and a focal position control section configured to control the focal point moving mechanism to locate the focal point in a predetermined position in the orthogonal direction; a beam vibration mechanism control section configured to control the beam vibration mechanism to change an amplitude with which the laser beam is vibrated so that an irradiation range of the laser beam that is a distance between both outer sides of the beam spot in a vibration direction when the beam spot is located at both end portions in the vibration direction is constant, according to a position of the focal point in the orthogonal direction, when the focal position control section controls the focal point moving mechanism to change the position of the focal point in the orthogonal direction. a machining head configured to emit a laser beam; a focusing lens configured to focus the laser beam to irradiate a sheet metal with the laser beam so as to form a beam spot (Bs) on a surface of the sheet metal; a moving mechanism (22, 23) configured to relatively move the machining head with respect to the sheet metal, along the surface of the sheet metal; a beam vibration mechanism configured to vibrate the laser beam when the sheet metal is cut by the irradiation of the sheet metal with the laser beam while the machining head is relatively moved by the moving mechanism (22, 23); characterised in that the laser machining apparatus further comprises: a focal point moving mechanism configured to move a focal point of the laser beam with which the sheet metal is irradiated, in an orthogonal direction orthogonal to the surface of the sheet metal; and a focal position control section configured to control the focal point moving mechanism to locate the focal point in a predetermined position in the orthogonal direction; a beam vibration mechanism control section configured to control the beam vibration mechanism to change an amplitude with which the laser beam is vibrated so that an irradiation range of the laser beam that is a distance between both outer sides of the beam spot in a vibration direction when the beam spot is located at both end portions in the vibration direction is constant, according to a position of the focal point in the orthogonal direction, when the focal position control section controls the focal point moving mechanism to change the position of the focal point in the orthogonal direction. a focal point moving mechanism configured to move a focal point of the laser beam with which the sheet metal is irradiated, in an orthogonal direction orthogonal to the surface of the sheet metal; and a focal position control section configured to control the focal point moving mechanism to locate the focal point in a predetermined position in the orthogonal direction; a beam vibration mechanism control section configured to control the beam vibration mechanism to change an amplitude with which the laser beam is vibrated so that an irradiation range of the laser beam that is a distance between both outer sides of the beam spot in a vibration direction when the beam spot is located at both end portions in the vibration direction is constant, according to a position of the focal point in the orthogonal direction, when the focal position control section controls the focal point moving mechanism to change the position of the focal point in the orthogonal direction.