1. An image filtering apparatus, comprising: a processor: configured to calculate depth values of each pixel in depth images, and infrared ray (IR) intensity values of each pixel from IR intensity images; configured to change a filter parameter for each pixel in the depth images to reduce noise of the depth images based on the depth values and the IR intensity values; and configured to apply a window determined from the filter parameter to the depth images, wherein the filter parameter for each pixel in the depth images is determined according to an amount of noise included in a pixel corresponding to the filter parameter, wherein the processor is configured to change as the filter parameter, a similarity with respect to a block included in the window, wherein the similarity with respect to the block is determined based on a reliability of a central pixel and a neighbor pixel within the block.