1. A work recognition device comprising: a whole-state observation time determination unit configured to determine, as a whole-state observation time, from among observation times of a plurality of first observation values generated by a speed sensor to represent respective movements of a hand of a user in chronological order, an observation time of observing a first observation value representing a predetermined movement of the hand, based on magnitudes of the plurality of first observation values and an angular difference between the plurality of first observation values; and an observation value selection unit configured to select a second observation value corresponding to the whole-state observation time determined by said whole-state observation time determination unit, from among a plurality of second observation values generated by an imaging unit to represent respective states in work of the user in chronological order.