  The leaderboard of Large Language Models (LLMs) in mathematical tasks has
been continuously updated. However, the majority of evaluations focus solely on
the final results, neglecting the quality of the intermediate steps. This
oversight can mask underlying problems, such as logical errors or unnecessary
steps in the reasoning process. To measure reasoning beyond final-answer
accuracy, we introduce ReasonEval, a new methodology for evaluating the quality
of reasoning steps. ReasonEval employs $\textit{validity}$ and
$\textit{redundancy}$ to characterize the reasoning quality, as well as
accompanying LLMs to assess them automatically. Instantiated by base models
that possess strong mathematical knowledge and trained with high-quality
labeled data, ReasonEval achieves state-of-the-art performance on human-labeled
datasets and can accurately detect different types of errors generated by
perturbation. When applied to evaluate LLMs specialized in math, we find that
an increase in final-answer accuracy does not necessarily guarantee an
improvement in the overall quality of the reasoning steps for challenging
mathematical problems. Additionally, we observe that ReasonEval can play a
significant role in data selection. We release the best-performing model,
meta-evaluation script, and all evaluation results at
https://github.com/GAIR-NLP/ReasonEval.
