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 and a lower roll set when a rolled material is rolled between the upper roll set and the lower roll set , the upper roll set having at least one roll and the lower roll set 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 and a lower roll set when a rolled material is rolled between the upper roll set and the lower roll set , the upper roll set having at least one roll and the lower roll set 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. <EOS>