It is well known that an antigen is damaged by a solvent during the microencapsulation process resulting in activity loss and poor reproducibility. In this study, novel double-walled microparticles containing hepatitis B surface antigen (HBsAg) were produced through a spray drying process. HBsAg was first encapsulated with hydroxypropyl cellulose (core microparticle). The core microparticles were then encapsulated again by poly [lactide-co-glycolide] resulting in the double-walled microparticles. By encapsulating HBsAg with hydroxypropyl cellulose in advance, it was found that HBsAg was protected from an organic solvent during the second encapsulation process with poly[lactide-co-glycolide]. Furthermore, the double-walled microparticle produced higher antibody titer than the single-walled microparticle when injected into guinea pigs. Finally the double-walled microparticle was compared with the alum formulation for feasibility as a hepatitis B single shot vaccine. The single shot of the double-walled microparticle was at least comparable with the two shots of the alum formulation in producing antibody. It resulted mainly from the HBsAg protective ability of hydroxypropyl cellulose against a solvent during the encapsulation process and the natural infection mimetic type of HBsAg release from the double-walled microparticles.