The present invention provides a cement setting accelerator comprising 100 parts by weight of a sintered body, 5 to 70 parts by weight of an alkali metal carbonate powder and at most 170 parts by weight of a lime powder and a method of manufacturing the same. The sintered body contains a predetermined ratio of 3CaO.2Na.sub.2 O.5Al.sub.2 O.sub.3, Na.sub.2 SO.sub.4 and Na.sub.2 O.Al.sub.2 O.sub.3. Alternatively, a predetermined ratio of 3CaO.2Na.sub.2 O.5Al.sub.2 O.sub.3, Na.sub.2 SO.sub.4 and 4CaO.3Al.sub.2 O.sub.3.SO.sub.3 are contained in the sintered body. Further, a raw material mixture, which is not sintered and equal in the chemical composition to the sintered body noted above, may be used in place of the sintered body. Setting and hardening of a cement paste is markedly promoted by adding a small amount of the cement setting accelerator of the present invention to the cement paste. Also, the initial setting time of the cement paste can be controlled by controlling the amount of addition of the cement setting accelerator of the present invention.