Instrument for measuring flatness by using linear light source

The utility model discloses an instrument for measuring flatness by utilizing a linear light source, which comprises an emitting device and a receiving device, the emitting device comprises a base andan emitting part positioned above the base, the emitting part is connected with a base bearing, and the linear light source emitting light in parallel with the horizontal plane is embedded in the outer surface of the emitting part; the receiving device comprises a base with the same height as the base of the transmitting device and a height difference measuring part above the base, the surface ofthe height difference measuring part is provided with a plurality of evenly-distributed scale marks, and the zero scale marks are equal to the linear light source in height with the horizontal planeas the benchmark. The instrument for measuring the flatness by using the linear light source is simple in structure, and can accurately judge whether any two points on a plane are horizontal or not through the cooperation of th