A search index generation apparatus includes: an information manipulation monitor unit detecting an information manipulation performed by a user on a computer by monitoring the information manipulation of the user on the computer; an information manipulation database for accumulation of data relating to an information manipulation detected by the information manipulation monitor unit; and a task detection unit analyzing the data relating to the information manipulation accumulated in the information manipulation database, detecting a task of the user, identifying an information group processed in the task, and recording the data relating to the task in the task database.