The Gurnee Fire Department said the independent contractor was doing work near Country Club and Northwestern Avenues.
The worker was laying fiber optic lines and used a "ruler-type device," which was 25-feet-tall.
The fire dept. said the ruler device made contact with an energized ComEd line and shocked the worker.
The worker, who is in his late 20's, was taken to Vista Medical Center with life-threatening injuries, the fire department said.
No other information was available.