1. A task selection assistance apparatus for assisting a user to select a task, the task selection assistance apparatus comprising a task selection assistance server communicable with a portable terminal, the task selection assistance server including: task model storing means for storing one or more tasks each indicating an action to be taken by the user to solve the user's problem in association with one or more pieces of attribute information each indicating an attribute of a task; attribute candidate determining means for determining one or more attribute information candidates to be presented to the user from the one or more pieces of attribute information stored in the task model storing means; user selected attribute obtaining means for obtaining the one or more pieces of attribute information selected by the user from the one or more attribute information candidates determined by the attribute candidate determining means; and task candidate determining means for determining one or more task candidates to be presented to the user from the one or more tasks stored in the task model storing means, based on the one or more pieces of attribute information obtained by the user selected attribute obtaining means, wherein the one or more task candidates can be narrowed down with the one or more pieces of attribute information including: a domain that is subject location information indicating a location subject to a task; and a task phase, and wherein the task phase includes an executing phase and a planning phase, the task in the executing phase is expected to be accomplished in the domain, the task in the planning phase is expected to be accomplished in other locations than the domain, and the task which is expected to be accomplished in a location independent of the domain is applicable to both of the executing and planning phases.