Justin Bieber's been well-stocked on weed for a year -- and there's picture proof.
TMZ has obtained multiple photos of Justin's kitchen taken at the beginning of 2013 ... when Bieber was 18.
The photos show an elaborate weed set-up -- including a bong, a substantial amount of weed, and other paraphernalia.
TMZ published photos of Bieber holding a blunt in January 2013 ... the first pics ever of the singer toking what appeared to be weed.
The kitchen seems to be drug central ... Bieber's pal Khalil recently posted the pic of himself in the singer's kitchen, holding a styrofoam cup -- a marker of lean ... the drug we know Bieber's been seriously abusing for at least a year.
And of course, there's the infamous smoke room in the mansion.