A laser unit comprising: a plurality of multi-mode semiconductor lasers (21-1 to 21-12; 101) configured to output laser lights in multi-mode; an optical multiplexer configured to multiplex and output the laser lights; a plurality of multi-mode optical fibers (30-1 to 30-12; 102), corresponding to the plurality of multi-mode semiconductor lasers, the multi-mode optical fibers respectively connect the multi-mode semiconductor lasers (21-1 to 21-12; 101) to the optical multiplexer , each multi-mode optical fiber including a core portion , a cladding portion having a refractive index, formed at an outer periphery of the core portion , and a coated portion having a refractive index, coating an outer periphery of the cladding portion ; a first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) formed to the multi-mode optical fibers (30-1 to 30-12; 102) and bent with a predetermined bending length and at a predetermined first bending radius; a radiation portion (11; 31) formed on the coated portion at the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa), and configured to radiate heat of the multi-mode optical fibers (30-1 to 30-12; 102); and a second bending portion (30b; 102b), remote from the first bending portion, formed to the multi-mode optical fiber (30; 30-1 to 30-12; 102) between the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) and the optical multiplexer and bent at a predetermined second bending radius, wherein R1-5[mm]≤R2 and R1<R0 are satisfied where R0 [mm] is a minimum bending radius between the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) and the multi-mode semiconductor lasers (21-1 to 21-12; 101) of the multi-mode optical fiber (30; 30-1 to 30-12; 102), R1 [mm] is the first bending radius, and R2 [mm] is the second bending radius, and wherein the predetermined length of the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) is equal to or greater than πR1. a plurality of multi-mode semiconductor lasers (21-1 to 21-12; 101) configured to output laser lights in multi-mode; an optical multiplexer configured to multiplex and output the laser lights; a plurality of multi-mode optical fibers (30-1 to 30-12; 102), corresponding to the plurality of multi-mode semiconductor lasers, the multi-mode optical fibers respectively connect the multi-mode semiconductor lasers (21-1 to 21-12; 101) to the optical multiplexer , each multi-mode optical fiber including a core portion , a cladding portion having a refractive index, formed at an outer periphery of the core portion , and a coated portion having a refractive index, coating an outer periphery of the cladding portion ; a first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) formed to the multi-mode optical fibers (30-1 to 30-12; 102) and bent with a predetermined bending length and at a predetermined first bending radius; a radiation portion (11; 31) formed on the coated portion at the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa), and configured to radiate heat of the multi-mode optical fibers (30-1 to 30-12; 102); and a second bending portion (30b; 102b), remote from the first bending portion, formed to the multi-mode optical fiber (30; 30-1 to 30-12; 102) between the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) and the optical multiplexer and bent at a predetermined second bending radius, wherein R1-5[mm]≤R2 and R1<R0 are satisfied where R0 [mm] is a minimum bending radius between the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) and the multi-mode semiconductor lasers (21-1 to 21-12; 101) of the multi-mode optical fiber (30; 30-1 to 30-12; 102), R1 [mm] is the first bending radius, and R2 [mm] is the second bending radius, and wherein the predetermined length of the first bending portion (30aa-1 to 30aa-4; 102aa; 311aa) is equal to or greater than πR1. <EOS>