A variable dispersion slope compensator with a high-accuracy and a low-cost structure for compensating the dispersion slope compensation error accompanying variations in the zero-dispersion wavelength in transmission fibers in long-distance, high-speed WDM (wavelength division multiplexing) transmission systems. When the value by which the optical fiber dispersion slope (ps/nm/nm/km) is divided by the dispersion coefficient (ps/nm/km) is defined as the relative dispersion slope RDS (/nm), then the variable dispersion slope compensator includes a first dispersion compensation fiber group including at least two dispersion compensation fibers with a common relative dispersion slope; and a second dispersion compensation fiber group including at least two dispersion compensation fibers with a common relative dispersion slope different from the relative dispersion slope of the first group; and a patch cable group or an optical switching group for making an optional connection combination between the first and second dispersion compensation fiber groups.