The present invention provides a reticle defect inspection method and a reticle defect inspection apparatus capable of calibrating the offset and gain of a sensor amplifier using a product reticle even though black and white regions each sufficiently wider than a TDI sensor imaging area do not exist in the product reticle. An output of each pixel of the TDI sensor is amplified by the sensor amplifier. A bottom value of the amplified amount-of-light signal of each pixel is stored by bottom value storing means of offset/gain calibrating means, and a peak value thereof is stored by peak value storing means. The offset of each pixel is calculated by offset calculating means based on the bottom value of each pixel. The gain of each pixel is calculated by gain calculating means based on the offset of each pixel and the peak value of each pixel. The calculated offset and gain of each pixel are stored in a register and thereby the offset and gain of the sensor amplifier are calibrated.