Laser scanner for scanning, in particular airborne scanning, of an environment, comprising a laser transmitter for transmitting a transmission beam, a laser receiver for receiving the transmission beam reflected on the environment as a receive beam, a beam-deflection device arranged in the beam path of the transmission and receive beams (4, 7) in the form of a mirror pyramid that is rotatable about a rotational axis and has pyramid sides inclined relative to the rotational axis that each form a mirror facet (10, 11, 12), and a housing, in which the laser transmitter, the laser receiver, and the beam-deflection device are arranged and which comprises a bottom face and a top face (18, 19), a lateral shell which connects the bottom face and top face (18, 19) and has an inner width that is less than the housing height between the bottom face and top face (18, 19), and a window for the transmission and receive beams (4, 7), wherein the beam-deflection device is adjacent to the window and its rotational axis is oriented substantially in parallel with the bottom face, and wherein a deflecting mirror is arranged in the housing deflecting the receive beam from the beam-deflection device onto the laser receiver, characterized in that the window is in the bottom face, the laser receiver is arranged closer to the top face than to the bottom face (19, 18) and the deflecting mirror is arranged adjacent to the bottom face in the housing, wherein, for focussing the receive beam on the laser receiver, an optical receiving system is arranged in the housing in the beam path between the beam-deflection device and the laser receiver, which optical receiving system is an optical lens having a decentralized optical axis, and wherein the deflecting mirror further deflects the transmission beam from the laser transmitter onto the beam-deflection device, the optical lens having a cut-out, which is in parallel with said optical axis and spaced apart from said optical axis, for the transmission beam to pass through. a laser transmitter for transmitting a transmission beam, a laser receiver for receiving the transmission beam reflected on the environment as a receive beam, a beam-deflection device arranged in the beam path of the transmission and receive beams (4, 7) in the form of a mirror pyramid that is rotatable about a rotational axis and has pyramid sides inclined relative to the rotational axis that each form a mirror facet (10, 11, 12), and a housing, in which the laser transmitter, the laser receiver, and the beam-deflection device are arranged and which comprises a bottom face and a top face (18, 19), a lateral shell which connects the bottom face and top face (18, 19) and has an inner width that is less than the housing height between the bottom face and top face (18, 19), and a window for the transmission and receive beams (4, 7), wherein the beam-deflection device is adjacent to the window and its rotational axis is oriented substantially in parallel with the bottom face, and wherein a deflecting mirror is arranged in the housing deflecting the receive beam from the beam-deflection device onto the laser receiver, characterized in that the window is in the bottom face, the laser receiver is arranged closer to the top face than to the bottom face (19, 18) and the deflecting mirror is arranged adjacent to the bottom face in the housing, wherein, for focussing the receive beam on the laser receiver, an optical receiving system is arranged in the housing in the beam path between the beam-deflection device and the laser receiver, which optical receiving system is an optical lens having a decentralized optical axis, and wherein the deflecting mirror further deflects the transmission beam from the laser transmitter onto the beam-deflection device, the optical lens having a cut-out, which is in parallel with said optical axis and spaced apart from said optical axis, for the transmission beam to pass through.