A laser apparatus includes a plurality of laser modules each generating a laser line in a working plane. The laser modules are juxtaposed so that the laser lines generated by the modules combine into a single laser line. Each of the laser modules includes at least one laser line generator. The laser line generator includes two linear arrays of strips of laser diodes each emitting a focused laser beam. The two linear arrays are arranged parallel to each other so that the strips are staggered. The two sets of parallel laser beams generated by the two linear arrays of strips, respectively, are merged into a single laser line by a set of mirrors. The linear arrays of strips of laser diodes and the mirrors are arranged so that the two sets of laser beams trace optical paths of the same length before being merged into a single laser line.