Disclosed are a proton type .beta. zeolite in which an acid site showing a desorption peak with a range of .+-.100.degree. C. with a center of 330.degree. C. exists in a spectrum measured by the ammonia temperature programmed desorption method (NH.sub.3-TPD), and an amount of a strong acid site showing a desorption peak of 500.degree. C. or higher is controlled to 2.5 .mu.mol/g or less, a method for preparing the same, and a process for preparing a phenol compound by oxidizing a benzene compound with a peroxide in the presence of the proton type .beta. zeolite.