A Boolean entropy decoder including a decoding module, a buffer and an updating module is provided. The decoder sequentially generates a first boolean value, a second boolean value and a third boolean value. The first and second boolean values are generated during a same cycle. The decoding module requires a first bit amount while generating a first value corresponding to the first boolean value, and requires a second bit amount while generating a second value corresponding to the second boolean value. The buffer temporarily stores a bit segment in the bitstream to be provided to the decoding module. The updating module fetches a new bit segment according to the first bit amount and the second bit amount and updates the buffer. The decoding module selectively updates a value corresponding to the third boolean value after the buffer is updated.