To provide an excavation support apparatus which allows a construction machine to carry out linear excavation easily and precisely.

The excavation support apparatus is the apparatus that gives support for excavation work using a construction machine. The excavation support apparatus includes a floodlight 2 which emits laser light along a reference surface S, a light receiver 11 which has a plurality of light-receiving units for receiving laser light in its longitudinal direction and is fitted to an arm 4, a tilt sensor 12 which detects the angle of tilt of the arm 4, and a control unit which calculates an actual excavation depth H1 ranging from the reference surface S to the front end of a bucket 3, based on detection signals from the light receiver 11 and the tilt sensor 12, and compares the calculated actual excavation depth H1 with a preset specified excavation depth H3 to determine an excavation error H2.