Les Bleus topped Group E, but were unable to break down 10-man Ecuador in their final game, and this is where Giroud has urged his side to improve if they are to reach the quarter-finals.
"There are no more easy games," Giroud told talkSPORT. "You have to play at 100% to win. We are doing well, even if tonight we didn't score. It was a great satisfaction for us to go through.
"We have to improve in the last 16, though. We need to have much more killer instinct in the box."
France scored three against Honduras and put five past Switzerland in their opening two group games.