A technique for acquiring knowledge about past trouble (malfunction) handling cases in information systems, and for recommending handling methods based on trouble handling knowledge and symptoms of troubles when they occurs, comprises: a searching process 260 for obtaining candidates of handling methods for troubles requested to be handled by searching the trouble handling knowledge 270; a recording process for recording to a storing unit 505, 506 a history of handling methods executed for each symptom as handling history information 250; a priority assigning process 230 for assigning priorities to the handling method candidates obtained by the searching process, with reference to the handling history information; and a process 230 for returning to a handling request source the handling methods for the troubles requested to be handled after assigning priorities based on priority assignment information obtained by the priority assigning process. Aspects of the invention include the priority assigning unit assigns a higher priority to: a handling method candidate effective also to other symptoms; a handling method candidate included in larger numbers within the handling history information; a more recently executed handling method candidate; or a handling method candidate which is originally assigned with a higher priority.