Actor Manabu Oshio was arrested on suspicion of using the synthetic drug MDMA, police said.
Oshio, 31, tested positive for the drug known as "Ecstasy" in a urine test yesterday the police conducted in connection with a woman who was found dead at an apartment in Tokyo's Roppongi district on Sunday night.
The police questioned Oshio on a voluntary basis Monday as it was found that he was with the woman, in her 30s, at the apartment before she died.
Oshio was quoted as saying that he called his manager and left the apartment after the woman developed a problem in her health.
The police conducted the urine test on Oshio as he showed symptoms of drug addiction, including shaking of hands, during the questioning.
Oshio told the police he was not aware that the drug, which he said was given by an acquaintance, is illegal.
The police are investigating the cause of the woman's death and the possibility of a crime. An external wound was not found on her, the police said.
Oshio's office Avex Management Inc. terminated a contract with him yesterday.
Oshio, who is also the vocalist of the band LIV, married actress Akiko Yada in November 2006.