According to one embodiment, a sleep state estimation device attached to a user during sleep and used is provided. The device includes a first detector, a first estimation module, a second detector, and a second estimation module. The first detector is configured to detect a first signal, to estimate a first state of the user. The first estimation module is configured to estimate the user's first state, based on the first signal. The second detector is configured to detect a second signal to estimate a second state of the user other than the user's first state. The second estimation module is configured to estimate the user's second state by using the second signal, based on an estimation method determined in accordance with the first signal.
