Cathinone-type designer drugs are a newly-encountered drug family that has a β-ketophenethylamine skeleton. Recently, the abuse of these drugs has been increasingly common among young adults, and this has caused a serious social problem in many countries. Many of those drugs have become regulated by the Pharmaceutical Affairs Act, and some of them were later banned by the Narcotics and Psychotropics Control Act in Japan, depending on their structures. In this paper, a total of 98 standards of cathinone-type designer drugs were synthesized, and their EI-mass spectra were acquired by GC/MS, with and without trifluoroacetylation. For their free bases, a major fragment ion formed from the α-cleavage of the amine nitrogen was commonly observed. Also, a small fragment ion generated by the α-cleavage of the carbonyl group, followed by the elimination of CO was detectable. For the analogs having an N-alkyl chain longer than methyl group and/or the alkyl side-chain longer than methyl group, a characteristic ion formed from the α-cleavage of the amine nitrogen, followed by the elimination of the olefin moiety was observed. For the trifluoroacetyl derivatives, the intensity of fragment ion formed from the α-cleavage of carbonyl group significantly increased, while that of the fragment ion generated from the α-cleavage of nitrogen decreased, when compared with those of free bases. Also, the ion at m/z 110 was specifically observed for the cathinone analogs having a methylamino group. Those typical fragmentation patterns revealed by analyzing a series of analogs provide useful information for the characterization of cathinone-type designer drugs.