Roache, 81, has played lothario Ken Barlow in the series portraying life in a fictional northern English town since its first episode on December 9, 1960.
He was arrested at his home in northwest England over an allegation of raping an under-age girl between April and July 1967.
"An 81-year-old man from Wilmslow in Cheshire has this morning, Wednesday May 1, 2013, been arrested by Lancashire Constabulary on suspicion of rape," a Lancashire Police spokesman said.
He said the man would be interviewed during the course of the day.
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Roache issued an apology in March after appearing to suggest that sex abuse victims were being punished for past sins, and calling for anonymity for those accused of child sex offences.
In another interview last year Roache claimed to have slept with 1,000 women.
Guinness World Records lists "Coronation Street" as the world's longest-running soap opera following the cancellation in September 2010 of the US show "As the World Turns", which ran from 1956 on CBS.
British police have arrested a series of celebrities since sex abuse allegations against the late BBC presenter Jimmy Savile emerged last year, although the allegations against Roache are unrelated to Savile.
Top British publicist Max Clifford was charged on Friday with 11 counts of indecent assault while former glam rocker and convicted paedophile Gary Glitter, comedian Freddie Starr and radio presenter Dave Lee Travis have been arrested and bailed.
Veteran Australian-born entertainer Rolf Harris has been named by the British media as another of the men interviewed as part of the investigation, although police have never named him.