A state estimation device configured to estimate a state of a user of a mobile terminal having a display section configured to display an image, the state estimation device comprising: a sightline detection section configured to detect the user's sightline; and an estimation processing section configured to execute first estimation processing, wherein the estimation processing section has: a top-down measurement section configured to measure a top-down index value in the first estimation processing on the basis of the image displayed on the display section and the user's sightline detected by the sightline detection section, the top-down index value being correlated with an attention source amount that is allocated to top-down attention of the user with respect to the image; a bottom-up measurement section configured to measure a bottom-up index value in the first estimation processing on the basis of the image displayed on the display section and the user's sightline detected by the sightline detection section, the bottom-up index value being correlated with the attention source amount that is allocated to bottom-up attention of the user with respect to the image; and an estimation section configured to estimate that the user state is an attention function degraded state in the first estimation processing on the basis of the top-down index value measured by the top-down measurement section and the bottom-up index value measured by the bottom-up measurement section, wherein the top-down attention is an attention mechanism in which the user actively moves his/her sightline to an intended point, the bottom-up attention is an attention mechanism in which the user's sightline is passively attracted to a noticeable point, and the attention source represents attentiveness of the user in a quantitative manner, and wherein in the case where the top-down index value falls below a predetermined top-down threshold (TDth1), the estimation section is configured to estimate that the user is in a first attention function degraded state when the bottom-up index value does not fall below a predetermined bottom-up threshold (BUth1). a sightline detection section configured to detect the user's sightline; and an estimation processing section configured to execute first estimation processing, wherein the estimation processing section has: a top-down measurement section configured to measure a top-down index value in the first estimation processing on the basis of the image displayed on the display section and the user's sightline detected by the sightline detection section, the top-down index value being correlated with an attention source amount that is allocated to top-down attention of the user with respect to the image; a bottom-up measurement section configured to measure a bottom-up index value in the first estimation processing on the basis of the image displayed on the display section and the user's sightline detected by the sightline detection section, the bottom-up index value being correlated with the attention source amount that is allocated to bottom-up attention of the user with respect to the image; and an estimation section configured to estimate that the user state is an attention function degraded state in the first estimation processing on the basis of the top-down index value measured by the top-down measurement section and the bottom-up index value measured by the bottom-up measurement section, wherein a top-down measurement section configured to measure a top-down index value in the first estimation processing on the basis of the image displayed on the display section and the user's sightline detected by the sightline detection section, the top-down index value being correlated with an attention source amount that is allocated to top-down attention of the user with respect to the image; a bottom-up measurement section configured to measure a bottom-up index value in the first estimation processing on the basis of the image displayed on the display section and the user's sightline detected by the sightline detection section, the bottom-up index value being correlated with the attention source amount that is allocated to bottom-up attention of the user with respect to the image; and an estimation section configured to estimate that the user state is an attention function degraded state in the first estimation processing on the basis of the top-down index value measured by the top-down measurement section and the bottom-up index value measured by the bottom-up measurement section, wherein the top-down attention is an attention mechanism in which the user actively moves his/her sightline to an intended point, the bottom-up attention is an attention mechanism in which the user's sightline is passively attracted to a noticeable point, and the attention source represents attentiveness of the user in a quantitative manner, and wherein in the case where the top-down index value falls below a predetermined top-down threshold (TDth1), the estimation section is configured to estimate that the user is in a first attention function degraded state when the bottom-up index value does not fall below a predetermined bottom-up threshold (BUth1).