1. A method for diagnosing abnormal plasma discharge, comprising: a data obtaining step adapted to cause a data obtaining section to obtain a time-series data that fluctuates in accordance with the plasma conditions; a determinism condition assessment step adapted to cause a derivation section to derive a value representing a determinism condition for providing an indicator of whether the time-series data in the plasma is deterministic or stochastic, from the time-series data that have been obtained in the data obtaining step; and an abnormal discharge determination step adapted to cause an abnormal discharge determination section to determine that the plasma is under the abnormal discharge conditions, if the value representing the determinism condition derived in the determinism condition assessment step is less than or equal to a given threshold value, during the plasma generation; wherein the value representing the determinism condition includes at least one of a translation error that is calculated from the time-series data and a permutation entropy that is calculated from the time series data.