android file open

I want to open file on android. I tried to implement as following.

// cs script
public Start(){
    using(FileStream stream = new FileStream("sample.bin", FileMode.Open)){
        data    = new byte[stream.Length];
        stream.Read(data, 0, (int)stream.Length);
        ...
    }
}

And,i set data as following.

- StreamingAssets
  - sample.bin

But,the file could not be opened. How do I implement ?