The left-back was strongly linked with a transfer to Manchester United last summer, although reports suggest that he could sign a new contract at Goodison Park this week amid more speculation surrounding his future.
"You know how important he is for us," Martinez told Sky Sports News. "He is in the best moment of his career and has got a real maturity which allows him to think on the pitch and make good decisions.
"He's not just a player, but a real icon of our football club, so clearly we want him to stay as long as we can. There is nothing to announce at the moment, but the way he's playing, he's looking to try to progress and develop.
"He is a player that you can imagine everyone at the football club would love to see him enjoying his football here for a longer period."
Baines featured in Everton's 1-1 draw at West Bromwich Albion last night.