WASHINGTON — The No. 2 official at the Centers for Medicare and Medicaid Services, who supervised the troubled rollout of President Obama’s health care law, is retiring, administration officials said Monday.

The official, Michelle Snyder, is the agency’s chief operating officer. She is the second administration official to depart since problems at the website, HealthCare.gov, frustrated millions of people trying to buy insurance and caused political embarrassment to President Obama.

Ms. Snyder is in charge of the Medicare agency’s day-to-day activities and the allocation of resources, including budget and personnel. Technology experts who built the website for the federal insurance exchange reported to her, and she has been actively involved in the effort to fix the site’s problems.

Ms. Snyder’s departure follows that of the agency’s chief information officer, Tony Trenkle, who stepped down in November to take a job in the private sector.