A laser optical system using optical fiber transmission, includes a first optical fiber for transmitting laser light emitted from a laser oscillator, a collimator lens for collimating laser light emitted from the first optical fiber, a spherical array lens including a plurality of cells for converging laser light emitted from the collimator lens into a plurality of spots, a plurality of second optical fibers each having a smaller core diameter than the first optical fiber and configured to admit the laser light converged into the corresponding spot by the spherical array lens, the second optical fibers having output ends that have mutually parallel axial lines and are arranged linearly in a single row, and a linearization optical unit for shaping laser light emitted from the second optical fibers into laser light having a linear cross section at an illuminated surface.