To provide an excellent small-sized fiber stub type optical device which facilitates the alignment and of which the joint state of an optical isolator part does not change due to alignment with an LD, and to provide an optical module using same.

In the fiber stub type optical device S1, optical fiber 5 and 6 are disposed in each of two through-holes 3a and 3b divided by a groove 7 formed in a ferrule, one side end of each optical fiber is projected into the groove 7 while the side face of the one side end of each optical fiber is covered with a protect member 11 with a refractive index higher than that of a clad part composing each optical fiber, each of the one side ends of the optical fibers is optically connected with other through an optical isolator 2 disposed in the groove 7. The optical modules M is obtained by disposing a fiber stub type optical device S and an optical element 15 receiving or emitting light for the optical connection with a fiber stub type optical device S on a substrate 14, respectively.