A battery abnormality detection circuit includes: a SOC detection unit that detects a SOC of a secondary battery; an internal resistance detection unit that detects an internal resistance value of the secondary battery; a first state acquisition unit that acquires a first SOC and a first resistance value at a predetermined first timing; a second state acquisition unit that acquires a second SOC and a second resistance value at a second timing a storage unit that stores in advance relationship information indicating a correspondence relationship between a SOC and an internal resistance value of the secondary battery; a reference variation value setting unit that sets a reference variation value indicating an amount of variation from an internal resistance value corresponding to the first SOC to an internal resistance value corresponding to the second SOC on the basis of the relationship information stored in the storage unit; and a determination unit that determines that an abnormality has occurred in the secondary battery when an amount of variation from the first resistance value to the second resistance value is different from an amount of variation indicated by the reference variation value that has been set by the reference variation value setting unit.