A printer apparatus comprising: a recording sheet conveying block configured to hold a recording sheet and convey the recording sheet to a printer head through a path for conveying the recording sheet; a head block including the printer head configured to print characters, graphics or the like on the recording sheet; and a control circuit, wherein the recording sheet conveying block and the head block includes a light emitting element configured to emit light, a first light receiving element positioned on a same side as that of the light emitting element relative to the path for conveying the recording sheet and configured to receive the light reflected by the recording sheet conveyed by the recording sheet conveying block, and a second light receiving element positioned on a side opposite to the side of the light emitting element relative to the path for conveying the recording sheet to face the light emitting element so as to be able to receive the light from the light receiving element, wherein a control circuit is connected to the light emitting element, the first light receiving element, and the second light receiving element, wherein the control circuit determines, when the light is detected by the second light receiving element, that the recording sheet does not exist between the light emitting element and the second light receiving element, wherein the control circuit determines, when the light is not detected by the second light receiving element and is detected by the first light receiving element, that the recording sheet exists between the light emitting element and the second light receiving element, wherein the printer head is a thermal head, and the light emitting element and the first light receiving element are provided in the thermal head. a recording sheet conveying block configured to hold a recording sheet and convey the recording sheet to a printer head through a path for conveying the recording sheet; a head block including the printer head configured to print characters, graphics or the like on the recording sheet; and a control circuit, wherein the recording sheet conveying block and the head block includes a light emitting element configured to emit light, a first light receiving element positioned on a same side as that of the light emitting element relative to the path for conveying the recording sheet and configured to receive the light reflected by the recording sheet conveyed by the recording sheet conveying block, and a second light receiving element positioned on a side opposite to the side of the light emitting element relative to the path for conveying the recording sheet to face the light emitting element so as to be able to receive the light from the light receiving element, wherein a control circuit is connected to the light emitting element, the first light receiving element, and the second light receiving element, wherein the control circuit determines, when the light is detected by the second light receiving element, that the recording sheet does not exist between the light emitting element and the second light receiving element, wherein the control circuit determines, when the light is not detected by the second light receiving element and is detected by the first light receiving element, that the recording sheet exists between the light emitting element and the second light receiving element, wherein the printer head is a thermal head, and the light emitting element and the first light receiving element are provided in the thermal head.