给你几个例子你就明白了。
He likes music too.
He doesn''t like music either.
Does he like music either?
He also likes music .
He likes music as well.
He doesn''t like music as well.
总结：too 用于肯定句句末，either 用于否定句和疑问句句末，also 放在主语和动词之间，如果谓语是系动词，则放在主语之后，系动词之前,而且also 通常用于肯定句。as well放在句末，同时即可用于肯定句，也可用于否定句。
希望对你有帮助！