A screen printer which performs printing by moving solder which is placed on a screen using a squeegee (32, 42), the screen printer comprising: a head (34, 44), on which the squeegee (32, 42) is mounted; parallel movement means for causing the head (34, 44) and the screen to move relatively in a direction parallel to the screen; perpendicular movement means (36, 46) for causing the head (34, 44) and the screen to move relatively in a direction perpendicular to the screen; position detection means for detecting a relative position between the squeegee (32, 42) and the screen; optical detection means which is provided such that an optical axis position is capable of moving relative to the screen due to the parallel movement means, and which is for detecting the screen and the solder at the optical axis position in an identifiable manner; printing completion time control means (70, 71) for, when printing is completed, controlling the perpendicular movement means (36, 46) such that the squeegee (32, 42) and the screen move relatively in a direction perpendicular to the screen to a position at which the squeegee (32, 42) is at least separated from a state of being in contact with one end side of the solder in a printing direction, and, after the controlling is performed, controlling the parallel movement means such that the head (34, 44) and the screen move relatively in a direction parallel to the screen until at least another end side of the solder in the printing direction is detected by the optical detection means; and solder amount estimation means (70, 71) for estimating an amount of solder on the screen, characterized in that the estimation of the solder amount is based on the relative position between the squeegee (32, 42) and the screen which is detected by the position detection means when the printing is completed, and the relative position between the squeegee (32, 42) and the screen which is detected by the position detection means when the other end side of the solder in the printing direction is detected by the optical detection means. a head (34, 44), on which the squeegee (32, 42) is mounted; parallel movement means for causing the head (34, 44) and the screen to move relatively in a direction parallel to the screen; perpendicular movement means (36, 46) for causing the head (34, 44) and the screen to move relatively in a direction perpendicular to the screen; position detection means for detecting a relative position between the squeegee (32, 42) and the screen; optical detection means which is provided such that an optical axis position is capable of moving relative to the screen due to the parallel movement means, and which is for detecting the screen and the solder at the optical axis position in an identifiable manner; printing completion time control means (70, 71) for, when printing is completed, controlling the perpendicular movement means (36, 46) such that the squeegee (32, 42) and the screen move relatively in a direction perpendicular to the screen to a position at which the squeegee (32, 42) is at least separated from a state of being in contact with one end side of the solder in a printing direction, and, after the controlling is performed, controlling the parallel movement means such that the head (34, 44) and the screen move relatively in a direction parallel to the screen until at least another end side of the solder in the printing direction is detected by the optical detection means; and solder amount estimation means (70, 71) for estimating an amount of solder on the screen, characterized in that the estimation of the solder amount is based on the relative position between the squeegee (32, 42) and the screen which is detected by the position detection means when the printing is completed, and the relative position between the squeegee (32, 42) and the screen which is detected by the position detection means when the other end side of the solder in the printing direction is detected by the optical detection means.