A deranged customer jumped on a Brooklyn laundromat counter and stabbed a female worker Monday – all because his laundry wasn’t done on time, according to police and the business owner. 

The attacker reportedly flew into a fit of rage when he was told his $15.34 wash-and-fold laundry wasn’t ready and allegedly slashed the woman’s neck and arms inside the Bath Avenue business just before 2 p.m., according to another employee.

EMS rushed the victim, in her 50s, to NYU Langone Hospital Brooklyn in stable condition, police said.

“She’s still in the hospital,” the victim’s coworker told The Post Monday evening while standing beside the counter where the attack unfolded. “We don’t know. She [was] cut [in] the neck. Too much blood. It’s very scary.”

She said the suspect got “mad” and “crazy” when he was told his clothes weren’t ready when he came to pick them up. The laundromat had been busy and his wash was still in the machine, the woman, who asked not to be identified, added.

The noticeably shaken employee saw surveillance footage of the bloody assault after it happened and said she recognized the madman as a customer who comes every month or two. His mother lives across the street from the laundromat, she said.

The crazed customer — who cops said was wearing a gray shirt and white sneakers — took off right after the vicious assault and ran north on 21st Avenue toward Benson Avenue, the NYPD said.

The laundromat’s owner told a Post photographer that the man had dropped off items that morning and became enraged when they weren’t ready for pickup.

Calls made by The Post to a phone number listed on the suspect’s laundry ticket were not returned by Monday night.

The police investigation is ongoing.