Recently, quantum computers are putting to use practically. Then casino games will be played on quantum computers shortly, as casino games have been played on classical computers. Quantum gambling theory has been studied, and it often brings non-trivial consequences that classical theory can not explain. We proposed a quantum blackjack: we devised a quantum circuit reproducing classical blackjack and found the possibility of entanglement between strategies. This circuit can be realized in the near future where quantum computers are commonplace. Furthermore, we showed the player's expectation increases compared to the classical game, using quantum basic strategy, which is a quantum version of the popularly known basic strategy of blackjack.