A plant monitoring device according to an embodiment is provided with a determination unit and a display processing unit. The determination unit compares a first process value obtained in a time series from the first point of a subject being monitored in the plant and a corresponding limit value to determine the time when the first process value exceeds the limit value. The display processing unit causes a display device to display, in a time series, the first process value within a time range defined on the basis of the time obtained by the determination unit, and the corresponding limit value.