The self-guided molecular dynamics (SGMD) method, which was proposed recently to enhance the efficiency of conformational sampling, has been extended to the isothermal-isobaric ensemble. It was applied to the crystallization of argon fluid in a supercooled state, and verified that crystallization was considerably accelerated with a suitable parameter set for the SGMD method. The algorithm proposed here also works well in the case of pressure-induced crystallization. A series of examinations we have done elucidates the applicable targets that SGMD works effectively.