A roll state monitor device comprising: rolling force detecting means configured to detect rolling force of a monitored roll selected from an upper roll set (3a,4a) and a lower roll set (3b,4b) when a rolled material is rolled between the upper roll set (3a,4a) and the lower roll set (3b,4b), the upper roll set (3a,4a) having at least one roll and the lower roll set (3b,4b) having at least one roll; force variation value extracting means configured to extract a rolling force variation value (ΔP) which is a value of each rolling force for each rotation position of the monitored roll; and identification means configured to identify a roll eccentricity amount (y Tj, y T0, y T1, y Tn-1, y Bj, y B0, y B1, y Bn-1) based on the rolling force variation value (ΔP); wherein the roll state monitor device is characterized by recording means recording a plurality of roll eccentricity amounts (y Tj, y T0, y T1, y Tn-1, y Bj, y B0, y B1, y Bn-1) calculated from the identification means in accordance with a plurality of rotation positions of the monitored roll in a first rolling period which is determined in advance; and roll state determining means determining a state of the monitored roll in a second rolling period which is after the first rolling period, based on a normal roll eccentricity amount representative value (Δy peak, y max, y min) which is a first representative value calculated from the plurality of the roll eccentricity amounts (y Tj, y T0, y T1, y Tn-1, y Bj, y B0, y B1, y Bn-1) calculated by the identification means in the first rolling period, and based on the roll eccentricity amount (y Tj, y T0, Y T1, y Tn-1, Y Bj, y B0, y B1, y Bn-1) calculated by the identification means in the second rolling period. rolling force detecting means configured to detect rolling force of a monitored roll selected from an upper roll set (3a,4a) and a lower roll set (3b,4b) when a rolled material is rolled between the upper roll set (3a,4a) and the lower roll set (3b,4b), the upper roll set (3a,4a) having at least one roll and the lower roll set (3b,4b) having at least one roll; force variation value extracting means configured to extract a rolling force variation value (ΔP) which is a value of each rolling force for each rotation position of the monitored roll; and identification means configured to identify a roll eccentricity amount (y Tj, y T0, y T1, y Tn-1, y Bj, y B0, y B1, y Bn-1) based on the rolling force variation value (ΔP); wherein the roll state monitor device is characterized by recording means recording a plurality of roll eccentricity amounts (y Tj, y T0, y T1, y Tn-1, y Bj, y B0, y B1, y Bn-1) calculated from the identification means in accordance with a plurality of rotation positions of the monitored roll in a first rolling period which is determined in advance; and roll state determining means determining a state of the monitored roll in a second rolling period which is after the first rolling period, based on a normal roll eccentricity amount representative value (Δy peak, y max, y min) which is a first representative value calculated from the plurality of the roll eccentricity amounts (y Tj, y T0, y T1, y Tn-1, y Bj, y B0, y B1, y Bn-1) calculated by the identification means in the first rolling period, and based on the roll eccentricity amount (y Tj, y T0, Y T1, y Tn-1, Y Bj, y B0, y B1, y Bn-1) calculated by the identification means in the second rolling period.