This paper focuses on the ability of robots to summarize their long-term experiences and answer questions—that is, to verbalize robot experience. Unlike previous studies that apply rule-based systems or fine-tuned deep models to short-term experience data, which suffer from limited generalization and transferability, this study leverages a pre-trained, large-scale language model to verbalize long-term robot experience through zero- or few-shot learning. A hierarchical tree structure is derived from episodic memory (EM), representing raw sensory and proprioceptive data at lower levels and abstracted events as natural language concepts at higher levels. Based on user queries, the large-scale language model acts as an agent to interactively explore the EM, dynamically expanding tree nodes to find relevant information. This approach maintains low computational costs even with months of robot experience data. We evaluate the flexibility and scalability of our method using simulated domestic robot data, human-viewpoint video, and real-world robot recordings.