The 20th Busan Particle Physics Workshop will be held at Pusan National University from Dec. 3 to 5, 2009. Everybody who are interested in Particle theory and Astroparticle physics, especially graduate students, are welcome to participate in the workshop. All participants will be provided with the lodging and meals. The aim of the workshop is to bring the experts in the fields together with the graduate students and the post-docs so that they can review recent developments, exchange ideas, and search future directions in particle and astroparticle physics. The format of the workshop is very informal and ample time is given to discussions.