The present disclosure discloses a shoulder belt assembly and a baby carrier. The shoulder belt assembly is used on a seat of a baby carrier, and includes: a fixing belt, both ends of which are fixed to the seat; an adjusting component slidably arranged on the fixing belt; and an adjusting belt connected to the adjusting component in such a way that a length thereof is adjustable. The shoulder belt assembly of the present disclosure has advantages of various adjustment modes, simple structure, convenient operation and the like.