The present invention relates to a monitoring apparatus (101) for monitoring an ablation procedure. The monitoring apparatus (101) comprises an ultrasound signal providing unit for providing an ultrasound signal that depends on received echo series of an object (4) that is ablated. The monitoring apparatus (101) further comprises an ablation depth determination unit (103) for determining an ablation depth from the provided ultrasound signal. The ablation depth can be determined directly from the ultrasound signal and is an important parameter while performing an ablation procedure. For example, it can be used for determining the progress of ablation within the object (4) and for determining when the ablation has reached a desired progression.