Work on his own
 

"he always works on his own" is the same as "he always works by himself?:(

Yes. on his own is the same as by himself. But, since the context is work, it could also possibly mean that he is self-employed.

I disagree that they're the same, David. The first can imply that he works without needing to be managed or checked up on, and the second, that he works alone.

You make a very good point. Depending on context, they may or may not be the same.

Elkikuyo, ¿Nos puedes dar toda la frase para poder decirte bien si son iguales o no?