An image adjusting method is adapted to an image adjusting circuit. The image adjusting method includes following steps. An image signal is received and up-sampled to generate a first up-sampled image signal and a second up-sampled image signal. The first up-sampled image signal includes interpolated pixels and original pixels. Values of the interpolated pixels and the original pixels are detected, and a weight value is outputted according to the detection result. Whether the values of the interpolated pixels are adjusted or not is determined based on the detection result. According to the weight value, the second up-sampled image signal and the adjusted first up-sampled image signal are mixed to output a mixed image signal. An image adjusting circuit is also provided.