how much milk does your baby burp out? One way to estimate is to pour some water on the floor and then compare the amount that he spits out.
When does your baby spit out? Is it after bending over, or after activities like bathing, and diaper changing?
If so, maybe you'll want to be gentler with your baby?
Do try to burp your baby thoroughly if he spits out. Can try various ways. Can also let your baby sit in a bouncy chair to keep him in a more upright position.
Sometimes excessive spitting can also be due to overeating/feeding.