Objective Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. In contrast to neurocognitive measurements of inattention and impulsivity, there has been limited research regarding the objective measurement of hyperactivity in youths with ADHD. The purpose of the present study was to investigate the clinical effectiveness of a newly developed Robot-assisted Kinematic Measure for ADHD (RAKMA) in children with ADHD. Methods In total, 35 children with ADHD aged 5 to 12 years and 50 healthy controls (HCs) were recruited, and the parents completed the Child Behavior Checklist and the Korean ADHD Diagnostic Scale. RAKMA performance was represented by RAKMA stimulus-response and hyperactivity variables. We compared the RAKMA performance of those with ADHD and with that of HCs and also investigated the correlation between the RAKMA variables and ADHD clinical scale scores. Results Significant differences between the ADHD and HC groups were observed regarding most RAKMA variables, including correct reactions, commission errors, omission errors, reaction times, migration distance, and migration speed scores. Significant correlations were detected between various ADHD clinical scale scores and RAKMA variables. Conclusion The RAKMA was a clinically useful tool for objectively measuring hyperactivity symptoms in children with ADHD. Further studies with larger samples are warranted.