Horiuchi began using Excel to create art after he saw others using the program at work, he said to PC Online.
But Horiuchi never actually used Excel for office purposes, as it's intended to be used.
"I saw other people neatly drawing graphs, and I thought it seemed like Excel could be used to draw art," he told PC Online.
Horiuchi said he chose Excel since it comes preinstalled in PCs. Graphic design software was too expensive.
next slide will load in 15 secondsSkip AdSkip AdHoriuchi even found Excel easier to draw with than Paint.
Before Horiuchi retired, he wanted to try something new.
So he purchased a PC and began experimenting with Excel artwork, PC Online reports.
Horiuchi uses the Autoshape function in Excel to create his images.
He layers custom colored shapes to weave together an intricate image.
next slide will load in 15 secondsSkip AdSkip AdIf you look closely, you can tell that each flower petal is its own shape.
Horiuchi's work typically revolves around outdoor scenes.
Needless to say, he had no problem winning the Excel Autoshape Art Contest in 2006.
His work is available online, and has even been featured in the Gunma Museum of Art in Japan.
Now check out some impressive photos taken with smartphones...