Within several years development of high energy physics experiments, a large number of exotic hadrons have been reported, e.g., the hidden-charm pentaquarks P_c and P_cs, as well as candidates of doubly, fully charmed and charm-strange tetraquarks, etc. I review herein the exotic hadrons that have been systematically investigated in the framework of real- and complex-scaling range of a constituent quark model. Several exotic hadrons observed experimentally were well reproduced by means of a commonly extended variational approach, the Gaussian expansion method; moreover, their possible compositeness and other properties, such as their decay widths and general patterns in the spectrum, are discussed. Besides, I report also some theoretical predictions of tetra- and pentaquark states which have not been observed experimentally.