A routing method in an ad hoc network between a source node (S) and a destination node (M) to guarantee a required quality of service level between the source node and the destination node. The source node (S) sends a route request to the network, request containing required quality of service level and an initial value of cost function (Fg). A node receiving a route request sent by a neighbor node then refuses said request if node is not able to guarantee said required quality of service level, and sends over the network a route request containing required quality of service level and a value of cost function combining a value of the cost function received from a previous neighbor node and a value of The cost function calculated on a connection with a neighbor node. The destination node (M) sends a route response step by step to the source node (S) containing the cumulative value of the cost function (Fg) corresponding to a route formed by successive connections between the source node (S) and the destination node (M). The source node chooses the route between the source node (S) and the destination node (M) having the best cumulative cost function.