A rope holding a member of an avant-garde Japanese dance troupe snapped today during a performance of a ''dance of birth and death,'' dropping the performer six stories to his death before hundreds of spectators.

The performer, Yoshiuki Takada of the Sankai Juku dance company of Toyko, died at at Harborview Medical Center shortly after the accident, which occurred at the Mutual Life Building.

The company was performing a dance, the ''Jomon Sho'' (''Homage to Prehistory''), which involved four dancers hanging upside down from the top of a building and being lowered slowly to the ground. It has been given hundreds of times in cities around the world. The troupe was in Seattle for a series of performances at the University of Washington.

The company's dance style, called Butoh, was born in the 1960's and is performed by more than 40 Japanese companies.