Facetime switch(hand-off) button doesn't appear on my iPad (mini 6)

Hello 진훈,

Based on the information found at Hand off a FaceTime call to another device - Apple Support, you want to be sure that all the settings are correct:

Hand off a FaceTime call to another device

During a call in the FaceTime app , you can move the call to another device where you’re signed in with the same Apple ID.

Note: Your selected contact information for the call, shown in Settings  > FaceTime (below You Can Be Reached At), must match the selected contact information in Settings > FaceTime for the device you want to hand off to.

1. Make sure your other device is turned on, then tap the screen that’s showing the call.

A notification of the call appears on the Lock Screen (or in Notification Center) of the other device, along with the suggestion “Move call to this [device].”

2. Tap the notification to switch the call, or tap  at the top left of the screen, then tap .

A preview of the call appears, showing your camera, microphone, and audio settings.

3. Make sure the camera, microphone, and audio settings are the ones you want, then tap .

The call moves to the new device. On the original device, a banner appears confirming that the call was continued elsewhere, along with , which you can tap if you want to bring the call back.

Once everything is set up right, you should be able to hand off the FaceTime calls.

Have a good day.