George Lopez -- What Are You Doing with a Vaporizer?

George Lopez has very expensive taste in weed-smoking paraphernalia ... at least judging by the fancy vaporizer he was carrying around last night in Beverly Hills.

Lopez was leaving Mastro's Steakhouse at the time -- along with Don Cheadle and Anthony Anderson -- when our photog spotted the $300 Pax vape tucked under Lopez' arm.

But here's the thing ... Mastro's is one of the most papped steakhouses in L.A. ... and Lopez left the place with Cheadle and Anthony ... two huge stars ... so he HAD to know he'd be photographed.

Our photog called him out -- and Lopez responded, "Don't look at that" ... then joked about needing the vape to inhale some Vicks VapoRub.