The invention relates to the field of seedling transplantation and aims at providing a hole excavating mechanism of a transplanting machine. The hole excavating mechanism of the transplanting machine comprises a support, a driving device, a first rack, a first slide rail, a first slider and a hole excavating device. The first slide rail is horizontally fixed to the support. The first slider is matched with the first slide rail. The hole excavating device is fixed to the first slider. The driving device drives the first slider and the hole excavating device to horizontally move on the first slide rail. The hole excavating mechanism of the transplanting machine has the advantages that the hole excavating device moves backwards in the hole excavating process so that the forward movement speed of the transplanting machine can be counteracted, a hole excavating cone can be static relative to a ground ridge when moving up and down for hole excavation, it is avoided that the hole excavating device breaks a thin film, the hole excavating and transplanting effects are improved, the hole excavating device is driven through the first rack fixed to the support, the displacement of the hole excavating device and the hole excavating process are made to be performed at the same time all the time, and synchronous movement is achieved.