1. A user support apparatus comprising: a sensor group configured to detect at least one of a user's activity state and environment situation; a user information providing device configured to provide the user with information; and a user activity support agent configured to produce information to be provided in the user information providing device based on at least one of the user's activity state and the environment situation detected by the sensor group, thereby supporting the user's activity, wherein the user activity support agent includes: a target detection evaluation module configured to detect at least one of demand, desire, and instruction of the user in the form of a target based on at least one of the user's activity state and the environment situation detected by the sensor group, and to ask the user whether or not the target is desired by the user via the user information providing device to evaluate the user's reaction to the information; and an activity plan evaluation module configured to plan the target detected by the target detection evaluation module in such a manner as to realize the target by the user's activity group, and to provide the user with information suggesting the activity group via the user information providing device to perform at least one of monitoring and evaluation with respect to the user's reaction to the information from at least one of the user's activity state and the environment situation measured by the sensor group.