Megumi Igarashi, 42, who calls herself Rokude Nashiko which roughly translates as "bastard kid", was taken into custody on Saturday for distributing data that allowed recipients to make 3D prints of her vagina.
"She was released today," said lawyer Kazuyuki Minami, adding that Igarashi and her legal team were to hold a press conference later Friday.
It was not immediately clear if the artist would face criminal charges.
Igarashi had been trying to raise funds online to pay for the construction of a kayak, using a 3D printer, modelled on the shape of her genitals.
Igarashi's supporters said they were shocked by what they described as the police's unusually broad use of Japan's obscenity laws.
Japan has a notoriously vibrant pornography industry that caters to a vast array of tastes. But obscenity laws still forbid the depiction of actual genitalia, which usually appear censored or pixellated in images and videos.
The artist was arrested for "distributing data that could create an obscene shape through a 3D printer," a police spokesman told AFP earlier.
Before her arrest, Igarashi had collected about one million yen ($9,800) through an Internet crowd funding site.
In exchange for donations, she supplied data to supporters that would let them create 3D prints of her genitals.
The artist's arrest sparked protest among her fans and supporters, who started an online petition to demand her immediate release, as they criticised police for what they said was an attack on free expression.
If convicted, Igarashi could receive up to two years in jail or a fine of as much as 2.5 million yen, according to her lawyer.
