This paper presents the Open-Kind 3D Instance Segmentation (OE-3DIS) problem, which enables novel object segmentation without predefined class names. Existing open-vocabulary 3D instance segmentation (OV-3DIS) methods suffer from the limitation of relying on predefined class names during testing; OE-3DIS alleviates this limitation. We build a robust baseline model by leveraging the OV-3DIS approach and a 2D multimodal large-scale language model, and evaluate its performance using a novel Open-Kind Score and a standardized AP score, which assess the semantic and geometric quality of predicted masks and their associated class names. On the ScanNet200 and ScanNet++ datasets, we achieve significant performance improvements over the baseline model, and even outperform the previous state-of-the-art OV-3DIS method, Open3DIS.