The development of mobile broadband is remarkable and its access speed amounts to 150Mbps for 4G (LTE), which is similar to fixed broadband, and mobile broadband, consisting of 3G and 4G, is expected to play more important role. The purpose of this paper is to analyze factors promoting mobile broadband adoption by panel data analysis, focusing on smartphones such as Android and iPhone. This paper analyzes the factors affect the mobile broadband adoption in major six countries, such as the U.S., UK, France, Germany, Japan, and Korea, those cover more than fifty percent of total population and adoption ratio of OECD 34 member countries. The factors examined here include HHI and frequency auction as completion policy, FTTH adoption, FMC (Fixed mobile convergence), and launching Android and iPhone, in addition to economic variables such as price and income. Panel data analysis showed that smartphones, competition among telecommunication carriers observed by HHI and FTTH affect mobile broadband adoption. The estimation result of HHI also suggests mobile consolidation should be restrictive to promote mobile broadband adoption. This result provides important basis for competition policy on mobile broadband in each country.