Disclosed are a method and apparatus for processing a transmission signal using a window function that changes a spectrum characteristic of a symbol. A transmission apparatus includes a symbol generator that generate a plurality of consecutive symbols, and a symbol windowing processor that is coupled with the symbol generator. The symbol windowing processor applies a first window function and a third window function that uses a difference between the first window and a second window, and changes a spectrum characteristic of each of the plurality of consecutive symbols, and processes neighboring symbols from among the plurality of consecutive symbols of which spectrum characteristics are changed, such that the symbols partially overlap one another.