controller is connected or not

How to find that player is using a controller or mouse/keyboard in game. or how to find joystick is connected to computer.

For determining what controllers are connected, you could try Input.GetJoystickNames(). I don't believe there's any way to determine what input device is being used for a particular axis, but if you write your own input manager on top of the built-in input system, you can keep track of that yourself.