Every now and then, I kept getting reading about market maker. Well, in stock market, a market maker could be possible. However, how can a broker become a market maker? Is there any way that broker can manipulate the market price?
Not only possible, but commonplace.
Look in the brokers guide ubder TOOLS higher up this page
If your broker is your counter-party - which is almost always the case from a legal perspective - then technically they are acting as a market maker for you.
Is there any way that broker can manipulate the market price?
When a broker passes a price through to you they often (for non-ECNs) pad the bid/ask spread, which is their way of making money on the transaction. That is price manipulation. You no doubt are thinking in terms of the bigger picture market price - the one that is seen at the inter-bank level. From that perspective, you are correct. Retail brokers have basically zero influence.