Yes, unless he did not realise that there had been a mistake and has innocently spent the money in a way that he would not have done, thereby altering his position in reliance upon the bank's error.
Your question suggests that he has realised there was an error, and has not spent the money.
H still has to repay it regardless of whether he realised or not. If he genuinely did not realise the bank will probably be more understanding in how it's repaid and they may even choose to let him keep it but they are within their rights to demand payment.
The Bank's claim is for the return of money paid under a msitake of fact. There is a perfectly good defence to such a claim based on estoppel/change of position, as outlined in my answer. The answer is not always yes.
Tell your friend to spend it on cheap wine and Pink Floyd albums and worry about the consequences later.
Also, it's possibly quite important to spend it and claim that he/she didn't even realise that there was extra money in the account, so no extravagant lump sum sales/purchases.