A rotary laser apparatus includes a light-projection section configured to irradiate at least two fan-shaped beams extending in a fan-shaped form in a direction orthogonal to a rotary axis. The light-projecting section includes a laser beam source for generating a laser beam in a direction of the rotary axis, and a rotation-irradiating section configured for irradiating the laser beam from the laser beam source in directions orthogonal to the rotary axis. The rotation-irradiating section includes a plurality of penta prisms and a beam splitter. The plurality of the penta prisms are arranged in the direction of the rotary axis depending upon the number of the fan-shaped beams such that light-emitting directions of the respective penta prisms differ from each other or one another, and the beam splitter is configured to the laser beam as required the penta prism arranged above.