His comments came in response to a meeting that Rice held this week with a US government commission intended to prepare for a "democratic transition" in Cuba after Castro.
"I am going to tell you what I think about this famous commission: they are a group of shit-eaters who do not deserve the world's respect," Castro told the Cuban parliament.
"In this context, it does not matter if it was the mad woman who talks of transition - it is a circus, they are completely depraved, they should be pitied."
Castro's assessment of Rice and the commission came after comments on Thursday, when he called Michael Parmly, head of the US interests section in Havana, a "little gangster".
Parmly had criticised the Cuban regime at a speech marking International Human Rights Day.
|Condoleezza Rice: 'mad woman'|
"The Cuban regime's hurling of angry and often violent groups against pro-democratic dissidents is particularly disgusting," Parmly had said.
He had also accused Castro's government of acting like Nazis against Cuban dissidents.
Castro, 79, said during another speech to the National Assembly that he did not know who was worse, "that little gangster", referring to Parmly or "the previous gangster", James Cason, Parmly's predecessor who Castro had earlier described as a "bully".
'Cynical and provocative'
Earlier this week, a moderator on a state television discussion condemned "the cynical and provocative activities" of the two US diplomats.
The United States and Cuba broke off diplomatic relations in January 1961. The US interests section opened in September 1977, reoccupying the seven-story former US embassy building.