'Teen Mom' Amber Portwood -- Baby Daddy Sued for Being a Deadbeat RENTER!

While "Teen Mom" star Amber Portwood is busy rotting away in the big house, her baby daddy is on the verge of getting EVICTED from his house ... this according to legal docs.

Gary Shirley is being sued for eviction by Real Property Management. In their lawsuit, the company claims Gary stiffed them for rent on his 1,500-square-foot Indiana crib ... to the tune of $1,360.

RPM is not only looking to collect the money, but they want Gary evicted ASAP.

As for Amber, she's serving a five-year sentence stemming from a drug arrest last year, while Gary has been taking care of their 4-year-old daughter -- which would be harder if he gets kicked out of his house.

A hearing is set for February 13.