A method of checking an abnormality in oil pressure of a transmission control unit (TCU) may include determining whether an oil pressure signal transmitted from the TCU to an electric oil pump (EOP) device is normal, transmitting a specific oil pressure value to the EOP device, the specific oil pressure value being set for determining whether the oil pressure signal transmitted from the TCU is normal, determining whether an oil pressure corresponding to the specific oil pressure value is sensed at the EOP device, determining whether a decrease range of the oil pressure sensed at the EOP device belongs within a predetermined range when compared to the specific oil pressure value, and determining whether to perform abnormality control over a transmission by operating the EOP device at set minimum revolutions per minute when the decrease range of the oil pressure sensed at the EOP device is beyond the predetermined range.