A motion sickness estimation device includes: a line-of-sight oscillation detector to detect oscillation of a line of sight of an occupant by using an imaging device； an object oscillation detector to detect oscillation of an object located in the line of sight； an oscillation comparator to calculate an oscillation difference from the oscillation of the line of sight and the oscillation of the object； and a motion sickness determiner to determine, on a basis of the oscillation difference, whether the occupant is in a motion sickness state.
