A laser device (1A, 1B, 1C) comprising: N semiconductor laser array stacks (LS 1... LS N), where N is an integer of two or more, that are each configured to include a plurality of semiconductor laser arrays each of which arrays emits laser lights (La) from two or more light emission regions being arranged in a predetermined direction while having emission directions aligned and which arrays are stacked in a stacking direction intersecting the predetermined direction and the emission direction, and wherein each stack outputs the laser lights (La) respectively emitted from the plurality of semiconductor laser arrays as one luminous flux (L n); a first collimation portion that performs collimation in a fast axis direction for the laser lights (La) included in the luminous flux (L n); a prismatic optical system (10A, 10B, 10C) that allows the luminous fluxes (L n) which are respectively output from the N semiconductor laser array stacks (LS 1... LS N) and pass through the first collimation portion to penetrate therethrough, and shifts an optical axis of the luminous flux (L n) in a direction intersecting the optical axis so as to decrease an interval between the luminous fluxes (L n); and an imaging optical system; characterized in that the imaging optical system includes N imaging lenses (F 1 to F N) that condense the luminous fluxes (L n) respectively output from the N semiconductor laser array stacks (LS 1... LS N) within a plane intersecting a slow axis direction for each luminous flux (L n) and N Deflection optical elements (D 1 to D N) that deflect the optical axis of each of the luminous fluxes (L n) within the plane for each luminous flux (L n), wherein the N deflection optical elements (D 1 to D N) of the imaging optical system deflect each of the luminous fluxes (L n) so that the N luminous fluxes (L n) overlap each other at a predetermined position, and wherein the N imaging lenses (F 1 to F N) generate a light-condensing point of each of the luminous fluxes (L n) between the imaging optical system and the predetermined position. N semiconductor laser array stacks (LS 1... LS N), where N is an integer of two or more, that are each configured to include a plurality of semiconductor laser arrays each of which arrays emits laser lights (La) from two or more light emission regions being arranged in a predetermined direction while having emission directions aligned and which arrays are stacked in a stacking direction intersecting the predetermined direction and the emission direction, and wherein each stack outputs the laser lights (La) respectively emitted from the plurality of semiconductor laser arrays as one luminous flux (L n); a first collimation portion that performs collimation in a fast axis direction for the laser lights (La) included in the luminous flux (L n); a prismatic optical system (10A, 10B, 10C) that allows the luminous fluxes (L n) which are respectively output from the N semiconductor laser array stacks (LS 1... LS N) and pass through the first collimation portion to penetrate therethrough, and shifts an optical axis of the luminous flux (L n) in a direction intersecting the optical axis so as to decrease an interval between the luminous fluxes (L n); and an imaging optical system; characterized in that the imaging optical system includes N imaging lenses (F 1 to F N) that condense the luminous fluxes (L n) respectively output from the N semiconductor laser array stacks (LS 1... LS N) within a plane intersecting a slow axis direction for each luminous flux (L n) and N Deflection optical elements (D 1 to D N) that deflect the optical axis of each of the luminous fluxes (L n) within the plane for each luminous flux (L n), wherein the N deflection optical elements (D 1 to D N) of the imaging optical system deflect each of the luminous fluxes (L n) so that the N luminous fluxes (L n) overlap each other at a predetermined position, and wherein the N imaging lenses (F 1 to F N) generate a light-condensing point of each of the luminous fluxes (L n) between the imaging optical system and the predetermined position.