The present invention relates to a radial disk type ion mobility spectrometer, comprising: an ionizing chamber which is made of a cylindrical tube, and includes an inlet for supplying sample gas therethrough, an ionizing means for ionizing the supplied sample gas to generate ions having a predetermined polarity, and a slit formed by cutting away a part of a cylindrical wall corresponding to a predetermined width for discharging the ions therethrough; a shutter grid installed adjacent to the slit of the ionizing chamber for controlling passage of the ions through the slit; a drift chamber which is a hollow tube having a predetermined thickness and including an outer cylindrical wall having a predetermined diameter and an inner cylindrical wall having an inner diameter equal to an outer diameter to the ionizing chamber so that an annular space is formed between the inner and outer cylindrical walls, of which a part of the inner cylindrical wall corresponding to a width larger than that of the slit is cut away such that the ions passing through the slit can be introduced into the annular space through the cutaway part of the inner cylindrical wall, and of which the inner cylindrical wall is engaged with the cylindrical wall of the ionizing chamber in such a manner that the drift chamber communicates with the ionizing chamber through the slit and the cutaway part of the inner cylindrical wall; and a collector installed onto an inner surface of the outer cylindrical wall of the drift chamber for collecting the ions that have passed through the drift chamber.