Cops busted a pipe-wielding attacker who smashed a straphanger on the head, sending him tumbling onto the subway tracks in Bedford Stuyvesant, police said Tuesday.

Leon Sims, 25, of Brooklyn, walked up to the 35-year-old male victim, who was sitting on a bench waiting for a southbound C-train around 1:20 a.m. Sunday, and allegedly beat him over the head with a pipe.

The victim fell onto the roadbed of the tracks but was not struck by a train, authorities said. He was taken to Interfaith Medical Center in stable condition and treated for gashes to the head and a chipped tooth, authorities said.

Sims fled but police nabbed him early Tuesday and charged him with two counts of assault.