The article examines the issue of the responsibility of a securities trader on the stock market of Ukraine. It is emphasized that, firstly, securities trading is a professional activity on the stock market; secondly, the activity of a securities trader is subject to licensing, in connection with which its implementation is also subject to the relevant provisions of the licensing legislation, the violation of which involves the application of appropriate measures of influence to the person; thirdly, trading in securities has the characteristics of financial services, which must also be taken into account when determining the nature of the liability of the relevant entity. It is emphasized that a securities trader can bear "double" responsibility: for committing a violation in contractual relations with a client or other participants in legal relations, a securities trader can bear property liability, for non-compliance with the requirements of legislation in the field of securities trading activities - bear specific administrative economic sanctions within the limits of public and legal coercion. Scientific approaches to determining the nature of the securities trader's responsibility, the concept of "professional responsibility", are analyzed. A study of the economic and legal responsibility of professional participants in the securities market is conducted, examples from the judicial practice of Ukraine are given. The essence and signs of the professional responsibility of a securities trader are established, the division of the professional responsibility of a securities trader into general and special is revealed. It is emphasized that the lack of a license of a securities trader indicates the absence of signs of professional activity in the securities market, as well as the fact that transactions made without obtaining a license may be declared invalid.