In 2012, a series of insider trading by fund managers who were advised nonpublic information on incumbent public offerings of listed companies by tippers in securities companies who served as lead underwriters was exposed, which inflicted damages on reputation of Japanese capital market. In response to these public offering scandals, insider trading regulations are reformed in 2013, the new regulation has been implemented since April, 2014. Reform is addressed to two major issues. First, the reform act has newly prohibited insiders from tipping material nonpublic information to others or from recommending trading of a stock without tipping information, both conducts of which were not prohibited before unless the insider-tipper was aiding or abetting the tippee-trader. Second, the act has raised amounts of administrative monetary penalties and introduced a system of offenders name publication. This article analyzes above two issues from viewpoints of legislative history and regulatory effectiveness, and points several problems. As to the ban on tipping information or trading recommendation, the intention to encourage the tippee to make a profit by trading prior to publication is required. This requirement was imposed in order not to prevent legitimate communications in the course of business or Investor Relations activities of listed companies. Because these prohibitions are applied not to tippees but only to insiders, they will not prevent trading by tippees’ teppees effectively. Amounts of administrative money penalties against asset management firms are raised up to three month commissions received from the person who conducted the trading. The maximum amount of money penalty is set to the profits earned from the illegal conduct However, it is necessary to impose much monetary penalty than the profits in order to prevent illegal conducts effectively. When an employee of a securities company discloses information illegally, the company, not the employee, is imposed monetary penalty. In order to give investors alert, the reform act allows FSA of Japan to publish the name of the offender. Because publication of name is not a sanction against violator, the violator cannot dispute the publication. Considering that publication of name gives the violator disadvantage, a system by which the violator files an administrative suit to rescind the publication should be introduced. In concluding part, I overviews enforcement actions against insider trading, and point that the fundamental cause of insider trading on public offering information consists in the Japanese market condition where publication of public offering by a listed company reduces market price of the stock of the company in a great amount.