Very! Apple Pay is actually safer than using a plastic credit card. Every transaction on your iPhone, iPad, or Mac requires you to authenticate with Face ID, Touch ID, or your passcode. Your Apple Watch is protected by the passcode that only you know, and your passcode is 

required every time you put on your Apple Watch or when you pay using Apple Pay. Your card number and identity aren’t shared with the merchant, and your actual card numbers aren’t stored on your device or on Apple servers. 

When you pay in stores, neither Apple nor your device sends your actual card numbers to merchants. When you pay within apps and on the web in Safari, the merchant will only receive information like name, email address, billing and shipping addresses that you authorise to share to fulfill your order. Apple Pay retains anonymous transaction information such as approximate purchase amount. This information can’t be tied back to you and never includes what you're buying. Apps that use Apple Pay must have a privacy policy that you can view, which governs the use of your data.

Learn more about Apple Pay security and privacy.