Robotic soccer games, which have become popular, require timely and precise decisionmaking in a dynamic environment. To address the problems of complexity in a critical situation, policy improvement in robotic soccer games must occur. This paper proposes an adaptive decisionmaking method that uses reinforcement learning (RL), and the decision-making system for a robotic soccer game is composed of two subsystems. The first subsystem in the architecture for the proposed method criticizes the situation, and the second subsystem implements decision-making policy. Inspired by the support vector machine (SVM), a situation classification method, which is called an improved SVM, embeds a decision tree structure and simultaneously addresses the problems of a large scale and multiple classifications. When a variety of situations that are collected in the field are classified and congregated into the tree structure, the problem of local strategy selection for each individual class of situations over time is regarded as a RL problem and is solved using a Q-learning method. The results of simulations and experiments demonstrate that the proposed method allows satisfactory decision-making.