Explosive growth of mobile data traffic becomes an increasingly serious problem in cellular networks. Delayed Wi-Fi offloading is the concept to shift the delay-tolerant mobile traffic from cellular networks to Wi-Fi networks at the cost of additional delay. Existing studies mainly focused on a single-flow management or a multi-flow case without specified deadlines. In this paper, we address a multi-flow offloading problem in which a mobile user has multiple traffic flows whose loads and deadlines are different. More precisely, we formulate a multi-flow rate control based on a discrete and finite-horizon Markov decision problem. We develop a dynamic programming (DP)-based optimal rate control algorithm to maximize user satisfaction defined as offloading efficiency minus disutility due to deadline violations. Moreover, we propose a threshold-based rate control algorithm which requires low-complexity and low-memory but achieves high performance. Trace driven simulations based on measurements show that our proposed algorithms achieve high user satisfaction compared to existing algorithms.