Many business processes, which are abstracted to workflows, have time constraints such that their processing should be completed within their deadlines. New time management technologies are, therefore, required for high workflow throughput, which can maximize the number of workflow instances satisfying their deadlines.In this paper, we propose an efficient deadline assignment method and validate its usefulness with experiments. Especially, the method divides activity deadlines into two categories, namely hard and soft deadlines according to the characteristics of activities. This can improve workflow throughput increasingly.