A stroller is designed to have a multi-step foldable mechanism which includes a connector having holes for receiving a back support with a long slot, a locking member having a stepped protrusion, a blocker, a tubular projection and a plate, and a receiving member for pivotally receiving the back support and securely receiving a front support. After the back support is inserted into the connector through the tubular projection of the locking member and one of the holes of the receiving member, a resilient member is inserted into a bottom of the back support and is suspended within the back support by a pin inserted into the locking member and received within the long slot of the back support, such that, when the blocker is lifted upward by a cylindrical projection formed on an outer periphery of an outer tube which is enclosing an arm of a handle, the stroller is folded. When the plate formed integrally with the locking member is being lifted axially upward, the stepped protrusion will be entirely extracted from the hole of the receiving member and achieve a purpose of folding and enhancement of safety while the stroller is being folded.