Colloquial term for a stockbroker or securities firm, often with a slightly informal or old-fashioned feel. Used in everyday conversation and news.
彼は株屋に勤めている。
He works at a stockbrokerage.
株屋の話を聞いて株を買った。
I bought stocks after listening to a stockbroker.
Compound of 株 (stock, share) and 屋 (shop, dealer). The exact historical derivation is uncertain, but the word has been used since at least the early 20th century to refer to stockbrokers.