The Lotto Belisol rider triumphed on Friday in the third stage as he broke in clinical fashion to outstrip his rivals from a bunch sprint.
After a fine ride of 173.5 kilometers from Knokke-Heist to Beveren, Griepel strengthens his leading position in the overall standings.
Italy’s Danilo Napolitano, for the third day in succession, finished second after being pipped in the frantic sprint finish. Britain’s Adam Blythe finished third.
Saturday’s stage represents an individual time trial over 20 kilometers.