Apple Pay works with iPhone 6 and later in stores, apps, and websites in Safari; with Apple Watch in stores and apps (requires iPhone 6 or later); with iPad Pro, iPad (5th generation), iPad Air 2, and iPad mini 3 and later in apps and websites in Safari; and with Mac (2012 or later) in Safari with an Apple-enabled iPhone or Apple Watch.
You can find a list of all Apple Pay compatible devices here: